The Next Step for Generics
blog.golang.org
blog.golang.org
func (c Container(T)) Map(transform(type V)(T) V) Container(V)
But, as per https://go.googlesource.com/proposal/+/refs/heads/master/des... it looks like maybe they will allow additional type parameters in methods, which would be REALLY nice.
I think type parameters of methods will definitely get added since it's so standard and if anything more confusing to not have them.
I think it's interesting to observe that using the Result type is really not that much different from using a multiple return value - it's actually worse in some ways because you end up using "Unwrap" which can panic.
Agreed that multiple return is actually quite nice in many situations, although `Unwrap()` is generally only called after checking `OK()` and the real benefit is in using `Map()`.
a, err := DoCalculation()
if err != nil {
return err;
}
b, err := Transform(a)
if err != nil {
return err;
}
a := DoCalculation()
b := ResultMap(a, Transform)I've written a decent amount of code professionally in the first and second styles.
I sincerely prefer the second style, for reasons that are hard to articulate, maybe the aesthetic, the space, or something that I assume is equally as questionable.
After I stopped writing a lot of code, when I got pulled back in to debug or provide context long after the fact, in both cases, it was way easier in "real" code bases, to catch myself back up on things in the case that the code was of style 1, than when it was of style 2!
I may be alone in this sentiment, and I even regret that I have it.
I think there is also a bit of satisfaction in writing the code in the second example, especially when the example is a lot more complex than the one provided here.
Maybe it comes down to how much re-reading/maintenance your codebase actually needs. I wonder if coding convention/style has been mapped to the types of problems that code creates and the subsequent repair of those problems being dependent on the code style... I'm sure if I google it I'll find something :)
One reason I like go is it doesn't have all the bells and whistles that give too many choices.
Or we can learn to read them. Just treat types like a first class value. You either assign names to types like you do to values, or you can assign a name to a function that returns a type, this being generics.
That's an awful way to think about hard to read code. I could produce the most unreadable one liners you've ever seen in your life. We should condemn that and not blame it on others to "learn how to read".
Think about the audience when you code.
Most of the time I hear about "hard to read code" is "pattern I don't currently have a mental model for". We didn't move on from COBOL by letting that be a deterrant.
class Result<T>
{
bool IsSuccess {get; set;}
string Message {get; set;}
T Data {get; set;}
}
It may frustrate coworkers who need to edit the code.
It adds another dependency into your workflow.
E.g.
libraryA.Result struct {
Err error
Data SomeDataType
}
libraryB.Result struct {
err string
Data SomeDataType
}
func (r libraryB.Result) Error() string {
return r.err
}
Let your caller bring their own error type and instantiate your library code over that.
At $work we definitely have examples where we care about preserving errors, and if that tool were implemented in Go a solution like a Result struct containing an error instance and a data type instance could make sense.
I love multiple returns/errors. I find that I never mistakenly forget to handle an error when the program won't compile because I forgot about the second return value.
I don't use go at work though, I use a language with lots of throw'ing exceptions, and I regularly miss handling exceptions that are hidden in dependencies. This isn't the end of the world in our case, but I prefer to be more explicit.
golang is not a modern language (how old it is is irrelevent), and the people who designed it did not have a proper language design background (their other accomplishments are a different matter).
Having worked on larger golang code bases, and I've seen several times where errors are either ignored or overwritten accidentally. It's just bad language design.
> people who designed it did not have a proper language design background
Irrelevant.
> It's just bad language design.
try { ... } catch(Exception ex) { ... }
The error here is explicitly handled, and cannot be accidentally ignored. Unlike golang where it's quite easy for errors to go ignored accidentally.
Each language has its wonks.
It's not similar to that at all. Without it, the exception bubbles up until it gets caught somewhere, or crashes the program with a useful stacktrace.
With golang, it just goes undetected, and the code keeps running with corrupt state, without anyone knowing any better.
If you care with go, use errcheck.
class Query {
class QueryResult {
Exception error;
Value result;
}
public QueryResult query() {
try {
return doThing();
} catch(Exception e){
return new QueryResult(error, null);
}
}
}
It's about the default error handling method being sane. In exception based languages, an unhandled error bubbles up until it reaches a handler, or it crashes the program with a stacktrace.
Compare to what golang does, it's somewhat easy to accidentally ignore or overwrite errors. This leads to silent corruption of state, much worse than crashing the program outright.
Gorm isn't using the default error handling.
I've seen a bunch of code that does the equivalent of the Java I posted above. Mostly when sending errors across the network.
fmt.Println("foo")
And I was referring to accidental ignoring. I've seen variations of the following several times now:
res, err := foo("foo")
if err != nil { ... }
if res != nil { ... }
res, err = foo("bar")
if res != nil { ... }>The following line in golang ignores the error:
fmt.Println("foo")
a := func() error {
return nil
}
a()
go-lint: Error return value of 'a' is not checked (errcheck)
res, err := foo("foo")
if err != nil { ... }
if res != nil { ... }
res, err = foo("bar")
if res != nil { ... }
go-lint: ineffectual assignment to 'err' (ineffassign)That's the issue with the language, there are so many special cases for convenience sake, not for correctness sake. It's obvious why it's excluded, but it doesn't make it correct. Do you want critical software written in such a language?
Furthermore, does that linter work with something like gorm (https://gorm.io/) and its way of handling errors? It's extremely easy to mis-handle errors with it. It's even a widely used library.
Perhaps more fundamental: it’s impossible to accidentally use an uninitialized “success” return value when the function actually failed, which is easy to do in C, C++, Go, etc.
func foo() (*SomeType, error) {
...
return someErr
}
...
result, err := foo()
if err != nil {
// handle err
}
// handle result
type Result struct {
Err error
Data SomeType
}
func (r *Result) HasError() bool {
return r.Err != nil
}
func bar() *Result {
...
return &Result { ... }
}
...
result := bar()
if result.HasError() {
// handle result.Err
}
// handle result
The Result<T> approach prevents you from accessing Data if you haven't handled the error, and it does so with a compile-time error.
Even with Go's draconian unused variable rules, I and my colleagues have been burned more than once by forgotten error checks.
https://github.com/kisielk/errcheck
https://golangci-lint.run/usage/linters/ has a solid set of options.
That's the point! I want language features!
I don't want to wait 6 years for the designers to bake some new operator into the language. I want rich enough expression so that if '?.' is missing I just throw it in as a one-liner.
Generics is one such source of richness.
It's also incredibly unsafe and why generics aren't enough. C++, Java, and so on have had generics for ages and with types like the one above, null pointer exceptions are incredibly common. Nothing prevents the user from attempting to retrieve the data without first retrieving the success status.
On the other hand, this improves on it dramatically:
enum Result<T, E> {
Success(T),
Failure(E)
}uh, you'd never get a null-pointer exception in C++ given the type that OP mentioned. Value types in C++ cannot be null (and most things are value types by a large margin).
class Result<T> where T: struct
{
...
}
A Result<T> that can only contain successful values doesn't seem very useful
int x = default; // x becomes zero
T x = default; // x becomes whatever the default value for struct isDon't think get;set is C++, though it breaks encapsulation.
A Result<T> that can only contain successful values doesn't seem very useful
See for example https://doc.rust-lang.org/std/result/enum.Result.html#method... in rust, https://docs.oracle.com/javase/8/docs/api/java/util/Optional... in Java, and https://en.cppreference.com/w/cpp/utility/optional/value_or in C++.
class Result<T>
{
bool IsSuccess {get; set;}
string Message {get; set;}
T Data {get; set;}
}[1] unfortunately not standardized yet https://github.com/TartanLlama/expected
class Result<T>
{
bool IsSuccess {get; set;}
string Message {get; set;}
T Data {get; set;}
}You: "C++, Java, and so on have had generics for ages and with types like the one above, null pointer exceptions are incredibly common."
jcelerier: "you'd never get a null-pointer exception in C++ given the type that OP mentioned."
You: "Then you can't construct it unless it's successful, no?"
Me: "The equivalent type in C++ [to what the OP mentioned] is std::expected". It is not possible to get a null-pointer exception with this type and yet you can construct it.
It sounds quite a lot like you're looking to be pointlessly argumentative, do I have that right?
1. The first, my original point was that a high quality type system enforces correctness by more than just having generics. There's no proper way in C++ to create this class and make a sum type - there's no pattern matching or type narrowing like can be done in languages with more interesting type systems and language facilities. Generics is just a first step to a much more interesting, safer way of writing code.
2. The second, my replies to folks who have corrected me, and I'll borrow your little paraphrase here:
> [Me]: "C++, Java, and so on have had generics for ages and with types like the one above, null pointer exceptions are incredibly common."
>
> jcelerier: "you'd never get a null-pointer exception in C++ given the type that OP mentioned."
>
> [Me]: "Then you can't construct it unless it's successful, no?"
I think this is exactly correct still. If it's impossible to create an instance of Result<T> without... well, a successful result, you may as well just typedef Result<T> to T, right? If it can't store the "failure" case, it's totally uninteresting.
If it _can_ store the failure case, making it safe in C++ is fairly challenging and I dare say it will be a little longer and a little less safe than a Result I can write in a few lines of TypeScript, Scala, Rust, an ML or Haskell derivative, and so on.
Now, I'd love to be proven wrong, I haven't written C++ for a while so the standard may have changed, but is there a way to write a proper enum and pattern match on the value?
It looks like this std::expected thing is neat, but can a _regular person_ write it in their own code and expect it to be safe? I can say with certainty that I can do that for the languages I listed above and in fewer than 10 lines of code.
The C++ answer to that is, well, this:
https://github.com/TartanLlama/expected/blob/master/include/...
I don't think it's a comparison.
the linked link has a ton of things that are "quality-of-life" things. For instance comparing two Result values efficiently (you don't want to compare two Result<T> bitwise, and you don't want the "is_valid" flag to be first in the structure layout to fallback on the automatic default of lexical order as that would sometimes waste a few bytes, but you want the "is_valid" flag to be the first thing being compared for instance. Do you know of a language that would do that automatically ?).
It also supports back to C++11 and GCC4.9 with various fixes for some specific compiler versions's bugs, supports being used with -fno-exceptions (so a separate language than ISO C++) - sure, today's languages can do better in terms of prettiness, but so would a pure-C++20 solution that only needs to work with a single implementation.
If you are ready to forfeit some amount of performance, for instance because you don't care that the value of your Result will be copied instead of moved when used in a temporary chain (e.g. `int x = operation_that_gets_a_result().or_else([] (auto&& error) { return whatever; });` 3/4 of the code can go away (and things will still likely be faster than most other languages).
They can just not exist. And C++ being C++, dereferencing an empty std::optional is UB. In practice this particular UB often leads to way worse consequences than more "conventional" null-pointer derefs.
Then chances are so are most if not all of the uses of generics OP criticises. The only "non-container" generics I can think of is session types where the generic parameter represents a statically checked state.
It doesn't hurt that static languages (TypeScript) or tools (mypy) that lightly lay on top of dynamic languages often do support sum types.
The good news is that many languages seem to be cozying up to them, and both the JVM (through Kotlin, Scala, et all) and .net (through F# or C# w/ language-ext) support them.
Even better news is that the C# team has stated that they want to implement Sum Types and ADTs into the language, and are actively looking into it.
I dislike dynamic languages where parameters and variables can take on any type -- it's rarely the case that same variable/parameter would ever need to contain a string, a number, or a Widget in the same block of code.
I find it much more freeing to have the compiler be in charge of exactness so I can make whatever changes I need knowing that entire classes of mistakes are now impossible.
And sum types aren’t for “radically different types”. You can define an error type to be one of different options (I.e. a more principled error code), or to represent nullability in the type system, or to indicate fallibility without relying on exceptions, etc.
Rust uses all of these to great effect, and does so because these sum types are generic.
It's a good software engineering principle to make control and data flow as streamlined as possible, for similar data. Minimize branches and special cases. Generics help with this, they hide the "irrelevant" differences, surfacing only the relevant.
On the other hand, if there are _actually_ different cases, that need to be handled differently, you want to branch and you want to express that there are multiple choices. Sum types make this a compiler-checked type system feature.
let v = match map.entry(key) {
Entry::Occupied(o) => {
o.get_mut() += 1;
o.into_mut()
}
Entry::Vacant(v) => {
update_vacant_count(v.key());
v.insert(0)
}
};
[0]: https://doc.rust-lang.org/std/collections/hash_map/enum.Entr...
Let's say you're opening a file that you think is a CSV. There can be several outcomes:
- the file doesn't exist
- the file can't be read
- the file can be read but isn't a valid CSV
- the file can be read and is valid, and you get some data
All of these are different types of results. You can get away with treating the first 3 as the same, but not the last. Without a tagged union, you'll probably resort to one of a few tricks:
- You'll have some sort of type with an error code, and a nullable data field. In reality, this is a tagged union, it's just that your compiler doesn't know about it and can't catch your errors.
- you'll return an error value and have some sort of "out" value with the data: this is basically the same as the previous example.
- you'll throw exceptions, which usually ends up with people writing code that forgets about the exception because the compiler doesn't care about it, and the code works 99% of the time until it completely blows up.
So, I mean, forget 'the next decade or two'; the majority of people are doing this right now; python and js are the probably the two most popular languages in use right now.
Will it end up in all statically typed languages? Dunno; I guess probably not in java or C# any time soon, but swift and kotlin support them already).
...ie. if your excuse for not wanting to learn it is that it's probably an edge case that most people don't have to care about now, and probably never will, you're mistaken I'm afraid.
It's a style of code that is very much currently in use.
Yes.
For example, some use cases: https://www.typescriptlang.org/v2/docs/handbook/unions-and-i...
This sort of code is very common.
I really don't know what more to say about this; if you don't want to use them, don't. ...but if your excuse for not using them is that other people don't, it's wrong.
They also tend to defer handling out into places where the context isn't always there.
The trend in language design does seem to be more broadly away from exceptions for this kind of thing and into generic pattern matching and status result types.
> Partially because people just get in the lazy habit of catch and rethrow RuntimeException, or catch and log, etc. when confronted with them.
After quite a while of thinking this way, I came to the conclusion that:
95% of the time, there's no way to 'handle' an error in a 'make it right' sense. Disk write failed? REST request failed? DNS lookup? There usually isn't an alternative to logging/rethrowing.
When there is a way to handle an error (usually by retrying?), it's top level anyway.
Furthermore, IO is the stuff that can just 'go wrong' regardless of how good the programmer is, and IO tends to sit at the bottom in most Java programs. This means every method call is prone to IOExceptions.
https://verraes.net/2014/12/erlang-let-it-crash/
If IOException on a read is truly happening, and it isn't just a case of a missing file, there are serious issues that aren't going to be fixed with a catch-and-log, or be able to be handled further up the call stack.
They're not popular in Java though, because the ergonomics is a lot worse than working with a Result type.
That it's mutable, at the very least!
For example, what if PHP could somehow detect string-concatenation in SQL queries and instantly `die()` with a beginner-friendly error message explaining to use query parameterisation from the very beginning: tens of billions of dollars of PHP SQL injection vulnerabilities simply never would have happened - and people who were already writing database queries with string-concatenation in VB and Java who gave PHP a try would then be forced to learn about the benefits of parameterisation and they'd then take that improved practice back to their VB and Java projects - a significant net worldwide improvement in code-quality!
[1]: https://blog.codinghorror.com/falling-into-the-pit-of-succes...
I've been writing in TypeScript for about 5 years now - and I'm in-love with its algebraic type system and whenever I switch back to C#/.NET projects it's made me push the limits of what we can do with .NET's type system just so I can have (or at least emulate as closely as possible) the features of TypeScript's type system.
(As for generics - I've wondered "what if every method/function was "generic" insofar as any method's call-site could redefine that method's parameter types and return types? Of course then it comes down to the "structural vs. nominative typing" war... but I'd rather be fighting for a hybrid of the two rather than trying to work-around an poorly-expressive type system.
struct Data {
idx: usize
// ...
}
struct Foo {
stuff: Vec<Vec<Data>>
}
struct Bar {
stuff: Vec<Data>
}
fn flatten_and_sort (foo:Foo, bar:Bar) -> Vec<Data> {
let mut output =
foo.stuff.into_iter()
.flat_map(|v| v.into_iter())
.chain(bar.stuff.into_iter())
.collect::<Vec<_>>();
output.sort_by(|lhs, rhs| lhs.idx.cmp(&rhs.idx));
output
}
let mut output: Vec<_> =
foo.stuff.into_iter()
.flat_map(|v| v)
.chain(bar.stuff)
.collect(); let mut output: Vec<_> =
foo.stuff.into_iter()
.flatten()
.chain(bar.stuff)
.collect();
let mut output: Vec<_> =
Iterator::chain(foo.stuff.into_iter().flatten(), bar.stuff)
.collect();
I definitely don't use generics if they can be avoided, and I think preemptive use of genericity "just in case" can lead to the situation you describe. If I'm not sure I'll really need generics I just start writing my code without them and refactor later on if I find that I actually need them.
But even if you only really care about generics for collections, that's still a massive use case. There's a wealth of custom and optimized collections implemented in third party crates in Rust. Generics make these third-party collections as easy and clean to use as first party ones (which are usually themselves implemented in pure Rust, with hardly any compiler magic). Being easily able to implement a generic Atomic type, a generic Mutex type etc... without compiler magic is pretty damn useful IMO.
- Promises
- Mutexes like Rust's Mutex<T> (would be much nicer than sync.Mutex)
- swap functions, like swap(pointer to T, pointer to T)
- combinators and other higher-order functions
s -> (s, a) is generic and a Functor (mappable - often conflated with a collection) but it's no collection!
In typescript I don't need generic too much / too complex, because the typing definition is more lax, and we can use dynamic in the very complex scenario.
I don't know which approach go is taking.
What about algorithms (sorts, folds, etc) on those containers? I write a lot of numerical code. It sucks to do multiple maintenance for functions that work on arrays of floats, doubles, complex floats, and complex doubles. Templates/Generics are a huge win for me here. Some functions work nicely on integer types too.
But I also have seen the problem with overuse of generics and other "advanced" type system features first hand (in libraries but also done by myself before I knew better).
Ex.
class ID<T> {
int id;
}
Now, this is just a simple example that probably won’t catch too many bugs, but you can do more useful things like have a phantom parameter to represent if the data is sanitized, and then make sure that only sanitized strings are displayed.
// UserID and PostID are distinct types
type UserID int
type PostID intI think the generic approach is a little bit better because of the flexibility, but this approach is still better than not having it at all.
It still provides a documentation benefit of course.
EDIT: Whoops, yes, as lentil points out, they are indeed distinct types not aliases. So it does provide the benefit of the Rust solution.
Your playground example didn't try to pass a UserID to a function accepting a PostID, but if you do that, you'll see the error:
For instance, if you have a function `f : Vec<a> -> SomeType`, the fact that `a` is a type variable and not a concrete type gives you a lot of information about `f` for free: namely that it will not use any properties of the type `a`, it cannot inspect values of that type at all. So essentially you already know, without even glancing at the implementation, that `f` can only inspect the structure of the vector, not its contents.
I agree with the sentiment that it is very easy to overuse genetics though there are scenarios where they are very useful.
For enterprise-level programming (which is the environment Go grew up in), a language that's too flexible is a hindrance, because you can always pay for more eng-hours, but you can't necessarily afford smarter programmers.
While I think I get the reasons for these decision in theory, make a simple-to-fully-understand language that compiles blazingly fast, I still feel it's a pity (most) these issues where not addressed.
> lack of proper sum types (C, C++, Java, JS)
Incidentally, Java and C# have addressed (or are in the process of addressing) both issues. Both languages/platforms are superior to golang in almost every conceivable way.
In any case, there already exist solutions in place:
Optional<Integer> foo;
//....
if (foo != null) {
foo.and_then(new Consumer () {
function accept(Integer foo) {
}
});
}To ensure assignment before use make it final.
It's been a WIP for years. Lets judge based on status quo rather than being disingenious.
I'm assuming you're talking about goroutines aka virtual threads/fibers whatever which are entirely different from actual threads.
EAP build - http://jdk.java.net/loom/
You could say that one could maybe copy the time-proven OCaml. But OCaml doesn't have a proven concurrency story, unlike Oberon and Modula-2 (yes, it had working coroutines back in 1992).
I also wish all these design decisions would not have been made in a new language, like they haven't been made in Rust. Unfortunately, the constraints under which creators of Go operated likely did not allow for such a luxury. As a result, Go is a language with first-class concurrency which one can get a grip of in a weekend, quick to market, and fast to compile. Most "better" languages, like Rust, OCaml, or Haskell, don't have most of these qualities. Go just fills a different segment, and there's a lot of demand in that segment.
Which is a mess. Sending mutable objects over channels is anything but "proven concurrency story".
Both Rust and Haskell (and OCaml, if we talk about concurrency and not parallelism) have way better concurrency story than Go. I don't care how fast one could start to write concurrent and parallel code if this code is error prone.
The only difference between Rust/Haskell and Go is that the former force you to learn how to write the correct code, while the latter hides the rocks under the water, letting you hit them in production.
That's an overstatement.
Also implicit nulls are not beneficent to anyone. And sum types could have made results (error/success) so much nicer. I see no reason to go with nulls at Go's inception, hence I call it a mistake.
Go clearly values "simple and practical" over "elegant". It seems to be quite successful at that.
Seems you are of the opinion if you do not find something practical no one else can.
Problem-space and learning styles play a huge role.
Not having generics and neither having very common tools doesn't seem very good. You will have to write a for loop for what is a simple function call in python or javascript or <insert modern language here>. Such detail easily interrupts reading / writing flow.
I think that most of the standard language features are based on generics, but you would never know it, as a user of those features.
I like Swift a lot, for many reasons, but generics design isn't one of these reasons.
Swift is sort of "generics for the masses." C++ is a lot more powerful, but also a lot more "in your face." I really do like the way that Swift allows generics to have implicit types.
1. People will eventually want generics 2. Retrofitting generics onto an existing language is hard and leads to unusual problems
(edit: I'm glad Go is doing this, but...Java learned this in 2004.)
1. https://arxiv.org/abs/2005.11710 2. https://news.ycombinator.com/item?id=23368453
I think TypeScript, Scala, Kotlin, C#, and various others I forget now proved that these things weren't a fad and could yield significant gains in productivity and code correctness.
Had Rob Pike been more forward looking (or hired Anders Hejlsberg or Guy Steele to design the language) or dipped further into the PL research, he might have been so bold himself. I don't think anyone can fault him for it, these were niche and minority views in 2010 and may not even be in the majority today.
I think at the same time, we see what happens when a new language has large corporate backing in more recent years. Swift more closely resembles Rust than Go in terms of its type system.
I've had a long career coding in C, C++, Java, Lisp, Python, Ruby... you name it I've done it. Go is my favorite most productive language by far for solving typical backend issues. My least favorite? Java by a HUGE mile.
It's pretty simple -- those of us who use those feature regularly in other languages know how valuable they are, and we miss them when they aren't there.
Is that really a problem? I think proper sum types to allow Result types that can encode many success/error states are so much nicer than an exception hierarchy. Rust and Kotlin did not go with exceptions, and for good reasons.
> C, C++, Java, Lisp, Python, Ruby... you name it I've done it.
Let me name a few: Rust, Kotlin, OCaml/Reason, Haskell, Elm. These languages carefully selected a set of features, the all have: no implicit nulls and sum types. And in your list non of them have those features. I really wonder what you think of these features when you've worked with them.
Kotlin very much did go with exceptions except for the Result type in coroutines which wraps a Throwable anyway and is only used for the border between the coroutine runner and the async functions.
If you see "unusual problems" with the design, then tell us what they are.
Otherwise it's just shallow pattern matching "Java added generics late, they had problems, Go added generics late therefore they'll have problems too".
Counterexample: C# added generics late and it's perfectly fine design.
The reason Go team is not rushing to implement generics is precisely so that the design makes sense, in the context of Go.
Over the years Ian Taylor wrote several designs for generics, all of which were found to not be good enough.
They are doing it the right way: not shipping until they have a good design and they didn't have good design when Go launched.
We all called this when Go was created, too.
(Not to disparage WASM, which has some nice ideas both on the technical and ecosystem level.)
Generics and Compile-Time in Rust
https://news.ycombinator.com/item?id=23534974
It's easy for spectators / bystanders to call something a mistake because you don't understand the tradeoffs. Try designing and implementing a language and you'll see the tradeoffs more clearly.
The overlooked thing is rustc produces poor quality LLVM IR which is also mentioned in FAQ.
And generics reduce amount of manual for loop juggling code one has to write. I don't think adding generics makes much of a difference.
LLVM is also slow in general. If you use it, it's likely the thing that's bottlenecking your language's compile-time unless you've done something insane like templates and `#include`, etc..
Inevitably it's the case that even if your source language doesn't do nearly as badly at the design stage when it comes to generics as C++ does, if you use LLVM your build stage is probably going to be unacceptably slow.
Agreed. But so is GCC. And I guess many of the 'zero cost' abstractions require some advanced optimizing compiler like LLVM to be zero cost (or move that complexity to compiler end).
They specifically mentioned the technical debt and poor LLVM IR Generation issue though. I wonder if it has yet gotten attention or fixed. Maybe @pcwalton knows.
Edit: well fast compile times at the expense of optimization. But that kind of proves the point.
var v chan int
var v Vector(int)
v := Vector(int)
v := make(Vector(int))
The solution to parameterized types which reference built-in operators is similarly minimal. You can't define the built in operators for new types. That's probably a good thing. Operator overloading for non-mathematical purposes seldom ends well.
They stopped before the template system became Turing-complete (I think) which prevents people from getting carried away and trying to write programs that run at compile time.
Overall, code written with this should be readable. C++ templates have reached the "you are not supposed to understand this" point. Don't need to go there again.
v := Vector(int){}
v := make(Vector(int))
For the same reason, I dislike `std::array<T, 5>` which puts the range type before the domain constraint. This is inconsistent with `std::map<int, T>` which puts the domain type before the range type, and `[](int x) -> T` which puts the domain type before the range type.
This introduces several parser ambiguities, esp. related to nested template types or types with multiple parameters. For instance, does `Foo Bar Baz` read as `Foo(Bar, Baz)` or `Foo(Bar(Baz))`?
var v chan(int)
var m map(keytype,datatype)
var v chan int
var m map[keytype]datatype
Map was always a bit too special in Go. Channels really are special; the compiler knows quite a bit about channels, what with "select", "case", and "go" keywords and their machinery. But maps are just a built in library object.
And yeah, operator overloading leads to utterly illegible code. Let's not go there!
E.g. in python these would correspond to a custom type implementing https://docs.python.org/3/reference/datamodel.html#object.__... & https://docs.python.org/3/reference/datamodel.html#object.__...
so if I defined my own map type (e.g. orderedmap[T] that kept things in the order they were added) then I'd need to write code for the [] operator to access an element, is that right?
I guess I'm not really sure how that differs from declaring orderedmap(T) (as it is in the proposal). Why do I need to overload one and not the other?
In Go, a pointer's integer value may not be stable since the GC may move the underlying data. This doesn't happen with today's runtime, but it may in the future.
Why does this matter? What if I want to make a hash table with the key being a pointer? The built-in map can just go ahead and hash the pointer itself (i.e. a 32/64-bit integer) since it's a part of the runtime and will be updated if the GC is changed. But a user map cannot do this: it would have to hash the actual value itself. Depending on your data, this could be significantly more expensive.
This doesn't stop anyone from implementing a hash table, but it may mean that it can't be as fast as the built-in map.
I'm not without concerns, but I'm struck by conflicting thoughts: I share the worry that implementing generics will negatively affect Go program readability which Go developers (rightfully) covet; when you have a hammer, everything looks like a nail. And yet, I also worry that the Go community is at risk of analysis paralysis on iterating the language in meaningful ways; the novel and innovative spirit that created Go must be harnessed to propel it into the future, lest it dies on the vine.
Old:
sum := 0
for _, x := range xs {
sum += xs
}
slices.Reduce(xs, 0, func(i, j int) int {
return i + j
})Reversing a slice of T. Copy and pasting this:
for i := len(a)/2 - 1; i >= 0; i-- {
opp := len(a) - 1 - i
a[i], a[opp] = a[opp], a[i]
}
reverse(a)
slices.Sum()I think the other replies to your comment point out the improvements that non-reduce-based versions of the code would bring, but I wanted to specifically call out reduce as being a pretty awkward function in other languages as well. So I think it's not a strong argument against generics (and the OP didn't mention wanting it in the first place); by and large functional methods like map, filter, reverse, etc are more readable; reduce is the exception that often isn't.
I wrote a fair bit of production Go code in my past, and missed many functional programming patterns. Didn't really miss reduce though. I'm glad that it seems like the ones I missed will become possible with this generics proposal.
And reduce isn't horribly unreadable, it's just a slight degradation compared to a for loop IMO. And the other functions are a large improvement.
type Null(type T) struct {
Val T
Valid bool // Valid is true if Val is not NULL
}
func Make(type T)(v T) Null(T) {
}
My only negative reaction is that throughout these proposals, I've not been a fan of the additional parentheses needed for this syntax. I can think of several syntaxes that would be more readable, potentially at the expense of verbosity.
I think that there are benefits when taking the time to gather feedback from people who actually use the language and make educated decisions with regards to language features instead of shoving them down in v1.
https://go.googlesource.com/proposal/+/refs/heads/master/des...
I can't find the actual code review for this. It seems to be hidden/private still?
This was the previous code review: https://go-review.googlesource.com/c/go/+/187317
The comment at the end is where I got the link to the new branch, but as an outsider, I don't have any good way to ask where the new code review is, so I'm leaving this comment here in hopes that a googler will see it and point me in the right direction.
Based on a link that's on the new branch's page, it might be CL 771577, but it says I don't have permission to view it, so I'm not sure.
The dev.go2go branch will not be merged into the main Go development tree. The branch exists mainly to support the translation tool, which is for experimenting with. Any work that flows into the main Go development will go through the code review process as usual.
I think that’s an unfortunate choice. Quite a few other languages use the term equatable for that, and have comparable for types that have =, ≤ and similar defined. Using comparable here closes the door for adding that later.
I also find it unfortunate that they chose
type SignedInteger interface {
type int, int8, int16, int32, int64
}
One couldn’t, for example, have one’s biginteger class reuse a generic gcd or lcm function.
The design draft refers to “constraints.Ordered”, so they’re definitely thinking about having both “comparable” and “constraints.Ordered”. Although, for consistency with “comparable”, I think it should be called “constraints.Orderable”.
My point was that “comparable” is not universally used in place of the “Ordered” term that the Go team is using, as you were seemingly implying. Ordered is a perfectly fine term for it.
You said:
> Using comparable here closes the door for adding that later.
But the door is not closed in any way. It’s just called “constraints.Ordered”, which is perfectly reasonable.
The `strings.Compare`[1] function is used to establish ordering, in the spec sense. You'd think they would name it "Order".
Similarly, the popular go-cmp[2] library provides `Equal` for equality, instead of `Compare`.
[1]: https://godoc.org/strings#Compare [2]: https://github.com/google/go-cmp
Think about how much planning and foresight goes into making a programming language, especially one that comes out of a massive top-tier tech company like Google. They deliberately chose not to include generics and (from what I remember when I wrote Go code) spent time + effort explaining away the need for them. Now the decision is being reversed, and it signals to me that they don't know what they're doing with the language, long term. As a developer, why do I want to hitch my carts to a language whose core visions are very clearly not correct or what people want?
If it's so damn obvious/you're so brilliant where's your proposal dated Jun 2010 (your 'decade lost') that "solves" generics?
It may not be surprising to everyone. Trouble is that the people who are not surprised now are the ones who sat back and only watched, preventing their knowledge from making it to the project.
Luckily for Go, a small team of domain experts decided to do more than sit back and their efforts are how the latest proposal was reached.
"Generics may well be added at some point. We don't feel an urgency for them, although we understand some programmers do."
...
"Generics are convenient but they come at a cost in complexity in the type system and run-time. We haven't yet found a design that gives value proportionate to the complexity, although we continue to think about it."
...
"The topic remains open"
They haven't flip-flopped whatsoever. Now that the language has more thoroughly been fleshed out and community has matured, and various proposals have come and gone, the discussion continues.
Languages that want libraries that go ten layers deep need to carefully manage things with sophisticated type systems and compilers that can cut through and inline all the abstractions so it still runs fast. Think rust, C++, haskell (all of which, not by coincidence, have long compile times).
Languages for writing applications and solving problems tend to have a flatter dependency tree and wider standard library (often including practical functionality like JSON parsers). Think erlang, Perl, PHP.
I used to think Go was in the latter category, but it seems to be getting pulled into the former category. Perhaps that's a reflection of Go developers using more layers of abstraction than they have in the past?
I don't think Go developers are using more layers of abstraction than they have in the past; they aren't smarter or more sophisticated than they were before -- RAFT was written in Go, for example.
Your observation is a good one, however; are there other ways that Go idiomatically flattens type hierarchies?
To be clear, I was not suggesting that more layers of abstraction reflect more sophisticated developers. Just that more layers require something in the language to help developers manage those layers without going insane.
There's a lot of wisdom in choosing a flatter approach when it makes sense.
I'll include ruby as well. It doesn't have a lot of "tools" per se, but if you're working on a nice codebase, it works out well even if using a lot of gems. Part of this is probably the unit testing/mocking, and part of it is that the code is just smaller. It does nothing to help you with performance though, so it can get really bad.
My experience with Java has not been great. I'm unconvinced that inheritance hierarchies are a good idea at all, or much of the other ceremony around Java-style OOP. Java uses JIT compilation, which can help with performance a lot.
If by "ontology" you mean "hierarchy", I'd caution you against that approach. Hierarchies enforce an order that is just not there in many cases. For instance, if you have an iPhone, would that be Hardware/Apple/iPhone or Apple/Hardware/iPhone? An iPhone is both Apple and Hardware, but there is no real order to those two -- yet if you try to put them in a hierarchy, then you must choose (and the choice will matter). I think interfaces/traits are much better. Both Go and Rust got this right.
Alternatively, use the bool values and rely on the zero value for missing elements: https://go2goplay.golang.org/p/E7yHQqAPseG
You could always offer a method that returns a slice of unique elements, which could then be ranged over.
However not to be just negative, I will certainly take the opportunity to provide my positive feedback as well, so looking forward to play with go2go.
Despite Go's success over the last 10+ years, have its designers concluded that the language is too simple? Is there no place for a simple statically-typed language like current versions of Go?
If not, then for those of us who particularly want a simple language, is dynamic typing the only option?
So, that's an interesting thing.
func Keys(type K comparable, V interface{})(m map[K]V) []K {
r := make([]K, 0, len(m))
for k := range m {
r = append(r, k)
}
return r
}
m := map[int]int{1:2, 2:4}
k := maps.Keys(m)
// Now k is either []int{1, 2} or []int{2, 1}. s := []int{1, 2, 3}
floats := slices.Map(s, func(i int) float64 { return float64(i) })
Type inference for generic function arguments
This is a feature we are not suggesting now, but could consider for later versions of the language.Every developer who discovers generics has this urge to be clever and write things that are hard to read and maintain.
Reading a Go codebase on the other hand is really a pleasure, this is due to the simplicity and straight-to-the-point aspect of the language, as well as the compile times. I really think Go had found a no-bullshit niche that it catered really well to, and I'm scared of what Go post-generics will look like.
Are there any other languages like Go that have no plans to move to generics?
PS: beautiful quote from rob pike: https://news.ycombinator.com/item?id=6821389
That's really unfortunate. I think a lot of the point of science (maybe even the entire point?) is to model the world and create taxonomies. Instead of being considered "busy work" or tedious, it should be held in the highest regard. Similar reasoning is why I think Rob Pike's opinion on generics is exactly wrong.
Go was already an oddball in not having generics when it came out, so I think it's unlikely that any new statically typed language will ever become popular. They're just too useful.
So instead of
func Print(type T)(s []T) { for _, v := range s { fmt.Print(v) } }
we would get
func Print<T>(s []T) { for _, v := range s { fmt.Print(v) } }
?
https://go.googlesource.com/proposal/+/refs/heads/master/des...
Foo<Bar>
Without generics, Go does not have a strong type system. It has a type system that verifies just enough to force you to work around it to do things that require generics, meaning that you don't get the benefits of verification because you've worked around it. You get the development speed of a statically-typed language with the type guarantees of a weakly-typed language: the worst of both worlds.
Gonum is good, but it can feel like a lot of the powerful abstractions in numpy and Eigen are difficult to replicate.
Whilst numpy and Eigen do "turn the magic up to 11" just a bit too much for my liking, I do like the idea of things like this:
interface Scalar() {
type float float32 int int32 int64
}
type DenseMatrix(type T Scalar) [][]T
func Identity(type T Scalar)(int size) DenseMatrix(T)
Seems like the go authors are still bent on the idea that generics are really not necessarily and that there is no such problem that can only be solved by generics. Then is the generic drafting only a thing because they have been pressured into it by the community? I wonder why Rob Pike one day decided that it’s okay to change a language he almost vowed to never change after the initial release.
> Methods may not take additional type arguments
While I can fathom the complications that arise, I'm hoping they can work past this restriction by launch.
- It gets you really garbage error messages, because the type errors are usually about something in the body of the template, wherever it tries to do something that the type you substituted doesn't support, rather at the offending call site.
- It hurts compile times (above and beyond proper generics), since you need to type check the generic function at every call site, rather than just once.
- It makes it easy to break interfaces, because exactly what is required of a type parameter isn't written down anywhere -- it's just whatever the body tries to do with it.
(Though it is also true that generics are certainly not a full substitute for macros. I would welcome some mechanism for doing codegen that didn't complicate the build system and was a bit lighter weight than what we have now).
Only early extremely non conforming compilers had macro-like template expansion.
Edit: although calling templates type level macros wouldn't be completely wrong.
Edit2: a better definition is that templates are type level functions: they take compile time values, types and other type functions and return values, types and type level functions.
The Template Haskell paper has some interesting things to say on the nature of C++ templates:
https://www.microsoft.com/en-us/research/wp-content/uploads/...
Unless you mean preprocessor macros in which case I'd rather cut myself.
What is he up to nowadays?
https://evrone.com/rob-pike-interview
> Rob: Although it's far from certain, after over a decade of work it looks like a design for parametric polymorphism, what is colloquially but misleadingly called generics, is coming in the next year or two. It was a very hard problem to find a design that works within the existing language and feels as if it belongs, but Ian Taylor invested a phenomenal amount of energy into the problem and it looks like the answer is now in reach.
Sounds like he took a welcomed step back. Hopefully the new leaders can deliver.
I'm rather excited..
type Enumerator(type T) func(yield func(element T))
func (loop Enumerator(T)) Select(f func(T) T) Enumerator(T) {
return func(yield func(T)) {
loop(func(element T) {
value := f(element)
yield(value)
})
}
}
func main() {
squares := Range(1, 3).Select(func(x int) int { return x * x })
squares(func(num int) {
fmt.Println(num)
})
}
// Output:
// 1
// 4
// 9
And, for generality, you should write the method actually as follows.
func (loop Enumerator(T)) Select(type R)(f func(T) R) Enumerator(R) {
return func(yield func(R)) {
loop(func(element T) {
value := f(element)
yield(value)
})
}
}
type checking failed for main
prog.go2:17:33: methods cannot have type parameters
> Although methods of a generic type may use the type's parameters, methods may not themselves have additional type parameters. Where it would be useful to add type arguments to a method, people will have to write a suitably parameterized top-level function.
> This is not a fundamental restriction but it complicates the language specification and the implementation.
For now, we have to write it as https://go2goplay.golang.org/p/mGOx3SWiFXq and I feel it rather inelegant. Good grief
This language is such a frustrating mess at times.
To anyone who has followed the Go development process at all, this proposal will not be a surprise. The previous proposal was also extremely conservative. Personally, I don't see any other way. Going full-blown generics in the style of Rust/Haskell/OCaml, for example, would drastically alter the language.
This is closer in scope to, say, Modula-3.
That said, the only feature I'd steal from Rust is sum types and getting rid of null. `nil` interfaces are the only language feature to actually cost me money and Option<T> is just better in every aspect, and Result<T> is much better than err == nil. I'd be perfectly happy with compiler blessed Option and Result types even if the larger language didn't support generics.
The type system may not always help you get your code out the door faster, but when you finally ship it, you have much easier time running it.
I have spent a lot of time in Rust getting carried away with type system stuff that is not required for the actual program I am writing. I realize this when I go over it a second time and reduce line counts drastically by replacing my gee-whiz generics with primitive types. This is balanced out by an equal number of times where I've reduced line counts drastically by using the advanced type stuff to reduce the repetition that comes along with using primitives to represent a type that has way more structure than the primitive.
I sometimes use the analogy of haiku versus short story.
You can pack a lot of meaning into a haiku, but few will be able to unpack it in the manner intended. A short story can get you to the point without filling a whole book to do so. And a lot more people can write a reasonable short story.
The question is, what is beyond generics? We need a humane alternative that still provides the type safe guard rails.
I do this too, but I’ve also come to realize that fresh perspectives and newly learned patterns may be more of the reason than being a little over zealous.
Edit: forgot to mention that this happens to me in most languages, not just rust.
In general I lean towards it not being a waste. That's not to say it's always useful for that project but it is usually useful as a learning exercise, that allows me to better identify similar patterns later (including whether generics are worth using compared to primitive types, in situations like that).
For example, I spent a good year or two forcing all of my iteration into functional styles. Now I am much better at coding in that style... and at knowing when a for loop is the more appropriate tool.
In C/C++, the base type system is so weak and squishy that everything redefines every type. You can no longer pass an 'int', but instead pass a "FOO_INT" or a "BARLONG" where FOO and BAR are trivial libraries that shouldn't need to redefine the concept of an integer.
Like C#, Rust has well-defined basic types, which eliminates a crazy amount of boilerplate and redefining the basics.
C# and Java might seem to have escaped that problem - but now it means that because `int` was defined back in 32-bit days programs can’t use `int` (System.Int32) when the intent is to use - what is presumably - “the best int-type for the platform” (I.e. C++’s fast-int types) - or the context (.NET’s arrays are indexed by Int32 instead of size_t, so you can’t have a Byte[] array larger than 2GB without some ugly hacks).
(I know this is moot for function locals as those will be word-aligned and so should behave the same as a native/fast int, but this isn’t guaranteed, especially when performing operations on non-local ints, such as in object instance fields).
Considering how seriously they take backward compatibility, the only way to do that would be to design a completely separate API, like they did with UWP. I'm 99.999% certain these macros are still being used somewhere out there. And who usually takes the blame when some badly written application stops working or compiling properly? Microsoft. (And I don't even like Microsoft.)
What I'm proposing isn't really a new API - but you're right about it having to be separate. It avoids the work of having to design a new API (and then implement it!) - what I'm proposing would keep the exact same Win32 binary API, but just clean-up all of the Win32 header files and remove as many #define macros and typedefs as possible - and redefining the headers for Win32's DLLs/LIBs using raw/primitive C types wherever possible.
There's just no need for "LPCWSTR" to exist anymore, for example. And I don't see anything wrong with calling the "real" function names (with the "W" suffix) instead of every call being a macro over A or W functions (which is silly as most of the A functions now cause errors when called).
This would only be of value for new applications written in C and C++ (which can directly consume Win32's header files) where the author wouldn't need to worry about missing macros. It would certainly make Win32 more self-describing again and reduce our dependence on the documentation.
Now we have Project Reunion as official confirmation of what has been slowly happening since Build 2018, as Microsoft pivoted into bringing UWP ideas into Win32.
Breaking backwards compatibility is a very high price to pay, as many of its proponents end up discovering the hard way.
I don't believe breaking back-compat was ever the problem: there were (and are) two main problems with UWP (and its predecessors[1]) going back to Windows 8:
* UWP were/are unnecessarily and very artificially restricted in what they could do: not just the sandboxing, but the app-store restrictions almost copied directly from Apple's own store.
* And because the then-new XAML-based "Jupiter" UI for UWP did not (and still doesn't, imo) ship with control library suitable for high-information-density, mouse-first UIs - and because XAML is still fundamentally unchanged since its original 2005 design with WPF in .NET Framework 3.5 - the XAML system is now far less capable (overall) than HTML+CSS in Electron now (the horror). Microsoft had a choice to maintain progress on XAML or let Electron overrun it for desktop application UIs - instead they've decided to keep XAML alive but for what gain? There simply isn't any decent exit-strategy for Microsoft now: they've just re-committed themselves to a dead-end UI system that needs significant amounts of re-work just to keep it competitive with Electron, while simultaneously using Electron for new headline first-party applications like Teams, Skype, Visual Studio Code, and more.
Microsoft has completely wasted the past ~10 years of progress they could have made on Windows and the desktop user-experience, letting Apple stay competitive with macOS while still funneling billions into iOS and iPad OS - further weakening the Windows value-proposition).
[1] Metro Apps, Modern Apps, Microsoft Store Apps, Windows Store Apps...
Skype uses React Native, and given that React Native for Windows bashes Electron in every talk that they give with its 300x overheard bar charts, expect that when React Native for macOS and Linux get mature enough, which MS is also contributing for, that eventually all Electron in use gets replaced with React Native.
Also React Native is built on top of UWP.
I can't speak for the iOS and Android mobile-apps, but the Skype software on my Windows 10 desktop is still an Electron app.
EDIT: This article from March 2002 says as much - Microsoft is moving away from React Native and sticking with Electron: https://www.windowscentral.com/latest-skype-preview-version-...
> Microsoft Skype is one of the largest React Native applications in the world.
https://blog.dashlane.com/exploring-react-native-on-windows/
With generics or typedefs (or a willingness to create lots of classes), you can be certain you never pass an Id<Foo> someplace that expects an Id<Bar>.
I write a lot of Rust nowadays, so I often need to keep myself in check and make sure I'm not getting sidetracked. When I'm writing internal code, the priority is to just get it done but still avoiding shortcuts. This is mainly avoiding .unwrap() / .clone() / taking care to handle Result correctly, as well as regularly running clippy to pick up the obviously silly stuff.
I find the most painful part of this strategy is when you want to revisit completed code to reduce copying as that generally requires a lot of type changes. At least when you get to this point though and haven't taken shortcuts, you've got functioning software and it should be fairly fault tolerant.
I spent 2 days implementing a (terrible) discriminated union struct type in C# (for types I don’t control, so I can’t just add an interface) rather than just return `Object` from a couple of methods.
Type systems need to be more expressive if we’re going to be able to increase developer productivity without costing program safety.
The .NET CLI itself places limits on what .NET-based languages can actually do: for example, structural-typing at method boundaries in CIL is only possible by having the compiler generate build-time adapter classes and interfaces - which means that methods accepting structural-types can’t be easily called by non-strucutural-typing-aware languages. The CLI also imposes single-inheritance - so a .NET language cannot implement multiple inheritance at all - and because non-virtual calls cannot be intercepted at all (without hacks like abusing .NET Remoting’s special-cases in the CLR) it’s not possible to have a “every call is virtual” system like Java’s in the CLR (note to self: find out how J# did it). Implementing Go-style composition is hamstrung by the fact we can’t patch the vtable at runtime either (reified vtables would be nice...).
I dare say it - but I think 2020 marks the decline of C# and the CLR because we’re held-back by decisions made over 15 years ago. .NET 5 isn’t showing any sign of significant improvements to the CLR’s type system or fundamental concepts.
A type system without native or at least low-impedance support for discriminated unions is, well, not a very good type system.
> Type systems need to be more expressive if we’re going to be able to increase developer productivity without costing program safety.
Lots of type systems support discriminated unions directly, or at least make it trivial to implement them. C# perhaps doesn’t, but that's a problem with C#, not typed programming in general.
This is interesting, because I generally feel like getting the types right actually IS most of the work that needs to be done, and once the types are correct the implementation code just follows from the available operations necessary. I've never used Rust, so perhaps it's different in this language (I understand memory management is quite onerous there?), but this is how things feel for me in C# or TypeScript.
My example for something that's simpler than Haskell but useful would be OCaml.
Most of my favourite design choices are the ones that make OCaml a functional programming language. So mostly not apt for Go. But here's a list of what I think one could adapt while staying true to the idea of a C-like language:
C had unions. They had some obvious problems. Go's solution was to get rid of them. OCaml instead went for discriminated unions (https://www.drdobbs.com/cpp/discriminated-unions/240009296) and made the compiler check that you are handling all cases correctly. In OCaml parlance, they are called algebraic data types.
C had null pointers. Go inherited them. OCaml uses the general mechanism of discriminated unions to represent cases like 'end of a linked list' or 'no data' or 'unknown' instead. And the compiler will check for you that you either handled those cases (when declared) or that you don't create those cases (when not explicitly declared to be there).
Some of C's constructs are generic. Like accessing arrays or taking the address of a value or dereferencing a pointer. To give an example, p works for a pointer of any type and does the right thing. And the compiler will tell you off, if you mix up the types.
As a user of C you can not add your own generic operations. You can use copy-and-paste or cast to and fro void or sometimes use function pointers in a clever way.
Go goes the same route. For example the built-in datastructures are generic, like maps or arrays.
Similar to C, a user of Go can not add their own generic operations. Go's sorting https://golang.org/pkg/sort/#Interface demonstrates what I mean by clever use of function pointers. (Note, how even that sorting interface still has lots of copy-and-paste when implementing and how it only really works for in-place sorting algorithms. I'm not sure how much trouble it would give in a multi threaded environment.)
I suspect Go's aversion to user-creatable generics comes from C++. C++'s templates confuse ad-hoc polymorphism and parametric polymorphism.
If C++'s unholy mess were the only game in town, Go's stance of restricting generics to the grownups (ie language implementors) would be perfectly reasonable.
OCaml carefully separates these two kinds of polymorphism.
Parametric polymorphism basically means 'this function or data structure works identically with any type'. That's what we also call generics. Eg the length of an array doesn't depend on what's in the array. (See https://en.wikipedia.org/wiki/Parametric_polymorphism)
When compiling you only need to create code once regardless of type. (Modulo unboxed types.)
Examples of ad-hoc polymorphism (https://en.wikipedia.org/wiki/Ad_hoc_polymorphism) are things like function overloading to do different things for different data types.
An infamous example are the bitshift operators from C whose cute looks got them roped into IO duty in C++.
In OCaml parametric polymorphism is handled as the simple concept it is. Ad hoc polymorphism (and unboxing for parametric polymorphism) are more complicated, and rightly make up the more complicated bits of OCaml types system.
Go could have gone with parametric polymorphism and left out ad-hoc polymorphism to stay simple.
(Parametric polymorphism synergises well with algebraic data types. Eg you can model the possibility of a null-pointer via an 'option' type, and have generic functionality to handle it. Same for the slightly richer concept of a value that's 'either an error message or a proper value'.)
But discussions about generics are a bit of a mine-field in Go.
Type inference. Go's type inference only goes one way, and is very limited. OCaml type inference goes backwards and forwards. Rust's system is perhaps a good compromise: it has similar machinery to OCaml, but they intentionally restrict it to only consider variable usage information from inside the same function.
(Generics restricted to parametric-polymorphism-only don't make type inference any harder.)
Back to something uncontroversial: Go allows tuples and pattern matching against them only when returning from functions and has lots of specialised machinery like 'multiple return types'.
OCaml just allows you tuples anywhere any other value could occur. You can pattern match against tuples and arbitrary other types. The compiler ensures that your pattern matching considers all cases.
I am sure there are more things to learn. But those few examples shall suffice for now. I feel especially strong about tuples as a wasted opportunity that wouldn't impact how the language feels at all. (From a practical point of view discriminated unions would probably make a bigger impact.)
- Written in Haskell
- Not a tool for manipulating Haskell
- With a substantial user base
- Other than Pandoc, xmonad, or shellcheck
Partial credit if you can name closed source software instead.
For Go, off the top of my head, Docker/K8s would qualify, but if we want to eliminate that, Hugo, Caddy, Gogs, etcd, fzf…
https://github.com/search?q=stars%3A%3E1000+language%3AGo&ty...
https://github.com/search?l=&o=desc&q=stars%3A%3E1000+langua...
I think I've heard the name darcs, but have no idea what it is or does. I may have heard of postgrest but I think the whole category of a thin layer over the DB is dumb, so I refuse to learn about it. :-) (If you want to talk to your DB, use the native SQL drivers. Don't just invent the same thing but as REST or GraphQL for no reason. Backend system should connect SQL to SQL. If you want a browser to be able to talk to your DB, then you will need auth and want bundling of calls and object translation and suddenly the thin translation layer isn't thin anymore.)
Anyway, the point is that Haskell has been around for a long time and is very popular with HN/Reddit users, but unlike Go and Rust, it has produced a very small amount of OSS.
I tried using darcs for a bit. But the designers were a bit too ambitious: they had an elegant concept to solve all rebases automatically at least in principle. Alas, the early implementations sometimes ran into corner cases that had exponential runtime. Which in practice meant that it hang forever for all a user could tell.
As far as I can recall, that behaviour is fixed now. But they missed their window of opportunity, when other dvcs became really popular. Like git.
Interestingly, git had the opposite philosophy: they explicitly only resolve simple conflicts in a simple way, and bubble up anything slightly more complicated to the user.
About SQL: Haskell users wouldn't want to use SQL directly. They want their compiler to yell at them when they get their database interactions wrong.
So they don't want some much to have a layer on top of SQL that hides things, but they'd rather want some support to forbid nonsensical SQL queries.
Interestingly, at one of my previous jobs we had 'relational object mappers' in our Haskell code. What that means is that we used relations as data structures inside our Haskell code, but had to interact with a mostly object oriented world on the outside.
Relations make fabulous data structures for expressing business logic. Take the leap in expressivity coming from eg dumb C to Python's ad-hoc dicts and tuples, and then imagine making a similar step again, and you arrive at relations.
Especially the various kinds of joins are good at expressing many business concerns. But projections and maps etc as well. Basically, everything that makes SQL useful, but embedded in a better language and just as a datastructure.
Codd's paper on relational algebra (https://www.seas.upenn.edu/~zives/03f/cis550/codd.pdf) is just as relevant to in-memory programming as it is to data bases.
> Anyway, the point is that Haskell has been around for a long time and is very popular with HN/Reddit users, but unlike Go and Rust, it has produced a very small amount of OSS.
The ML family of languages that Haskell is a part of has been around for even longer, and many of the beloved features of Haskell stem from that older legacy.
I don't have high hopes of the ML family becoming more mainstream. But I am really glad to see many advances born in the land of functional programming, and ML or Haskell in particular, making it out into the wider world.
The poster child is garbage collection. Which was invented for Lisp in the first place.
(You can do functional programming without garbage collection, but it requires much more finesse and understanding than they had when Lisp was young. And even then, garbage collection is probably still the right trade-off when you programme is not resource constrained.)
Garbage collection is pretty much the default for new languages these days. People expect a good rationale for any deviation.
More recently we have seen first class functions, closures and lambdas make it out into the wider world. Even Java and C++ have picked up some of those.
First class functions belong relate to a wider theme of 'first class' elements of your programming language. I remember that eg in Perl you had to jump through extra hoops to make an array of arrays. That's because arrays were not by default treated the same as any other value.
I think Python did a lot for the mainstream here: Python is pretty good at letting you assign many of its constructs (like classes or functions or ints or tuples etc) to variables and pass them around just like any other value. In the understanding of the Python community, they see that just as good OOP, of course.
Combinators like map and filter have become popular in mainstream languages.
Algebraic data types have made it to a few languages. With that comes structural pattern matching, and the compiler complaining when you miss a case.
Tuples are pretty much expected in any new language these days.
The very article we are commenting on talks about generics.
Immutable data types are something every new language is supposed to have thought about. Even C++ has const and Java has final. Go's designers were asked to justify their very limited support for immutability.
Many people go so far as suggesting immutability should be the default in new languages. (And you could very well imagine a dialect of C++ where 'const' is implied, and you need 'mutable' everywhere, if you want to override that.)
There's quite a few more examples. Of course, correlation is not causation, and so not everything that showed up in functional programming languages before it showed up in the mainstream means that the mainstream actually got it from FP.
---
In summary, you are right that Haskell has not been used in OSS or commercial products as much as eg Go, but I am just happy that the rest of the world is moving in the Right Direction.
If anything, you should have asked about the prospects of OCaml, shouldn't you? (Spoiler alert: they are grimmer than Haskell's.)
Mostly, Go is full of wasted opportunities. It would have perhaps been a worthwhile language had they come up with Go instead of C in the 1970s. https://github.com/ksimka/go-is-not-good is a good summary.
I would suggest having a look at D as an example of what an evolution of C could look. An evolution with fewer wasted opportunities.
We also used OCaml at Bloomberg quite a bit. (And they are still using it, but I'm not there anymore.)
But there's not that much more in the commercial OCaml world.
Haskell has actually a bit of a broader adoption. The open source library situation is also better.
(For the record, I like both OCaml and Haskell. And Janestreet are doing a great job.
And commercial and open source adoption are important. But they are not the end to every discussion.)
In my world, anything the type system doesn’t do for me, I must do myself in unit tests.
It’s actually possible to learn a type system and get good/fast at it. But typing out all those goddamn test cases never gets any easier, and updating them when the code changes is a nightmare.
When I was much younger, I was told by my elders that to a first approximation a function doesn't need a name because it's defined by its range and domain. If it's hard to discern what the function does just by the range and domain then your type system isn't powerful enough. This insight is as powerful as it is superficially wrong.
1) Consider easing functions in animation (see easings.net for examples). They all have domain and range "real numbers between 0 and 1", yet they are all meaningfully different.
2) Consider filters in audio processing. They all have domain and range "streams of real numbers", yet they are all meaningfully different. The fact that they have the same type is important - it allows composition of filters, which I'd hope would sound exciting to a typed programmer!
3) Consider sorting algorithms. Even under a very advanced type system, the domain would be "arrays of numbers" and the range would be "sorted arrays of numbers". Yet there are tons of sorting algorithms that are meaningfully different. The fact that they have the same type is important - it allows a sorting library to evolve without breaking applications.
See the common thread? Types enable mixing and matching functionality. If a type allows only one functionality, it's useless for that purpose.
I was thinking a similar thought: sine vs cosine. But I think that falls under 'superficially wrong'.
Can confirm, this happened to me in Java constantly. I once spent an hour writing a big utility class using generics, even though I needed it for only one type in the code. "What if I need it for something else? Copying the code and replacing the types is very inefficient!"
Turned out that Java, being Java, was unable to instantiate an empty array of a generic type, so the very elegant code in the utility class now meant having to handle a bunch of special null cases in the application. I actually left it in for a while, but thankfully changed my mind before merging it as I'm sure the team wouldn't have appreciated having to deal with even more null in unexpected places because I got attached to my shiny generic code.
In general, I agree with your sentiment. Though in some cases, an abstraction can be justified even when used only once.
Take the simple case of a function. Generally a function only communication with its surroundings via parameters and returned values. A function that respects those conventions makes reading code much easier, and can be worth it even if used only once.
In contrast, a code block inside a much larger stretch of code doesn't give the reader any explicit guidance one how it intends to interact with the rest of the system. Even if it's exactly the same code as in the function.
Similarly, a for-loop can do almost anything. But using map or filter immediately tells you that only a few things are possible here. Even a fold is more restricted than a general for-loop.
'Theorems for free' makes a very similar argument for generics. https://people.mpi-sws.org/~dreyer/tor/papers/wadler.pdf
This is especially true with Rust where you also need to consider who owns what data. With C# it’s much too to model things that make sense as a type zoo but where the more important problems like ownership and access patterns is lost in the cracks.
The typical sign in Rust is when you need a lifetime on a struct so you realize it has someone else’s data. That usually means I stop to think before progressing. In C# it’s very easy to miss that big red flag.
Obviously it’s always worth revisiting and simplifying a design, but I still don’t think the initial design or designs were a waste of time if it gave me an understanding of the problem space.
In Go I never felt that omg it misses some big features we're screwed, we're going to pay the cost of running that in Prod. All the services I worked on while not being perfect ran like a clock without issues on the long term, and it has to do with Go "simplicity", eventhough you never wrote the code you can actually jump into any code base without issues, there is no weird abstraction layer / complexity that takes you day to understand.
For me the fact that Go is a "simple" language is very powerful because on the long run it's much easier to maintain.
I like Rust a lot and I hope to get to use it more, but "added type safety at the expense of iteration velocity" is not a good tradeoff for my domain and I suspect many others (although its iteration velocity is improving monotonically!).
Rust: For code that isn't meant to be iterated upon, that must be safe/correct while also being performant.
Go: For code that is meant to be iterated upon frequently, that must be performant and easy to maintain.
I would like my tools to be written in Rust, and I would like to interface with them in Go.
But the same shoddy system is also constantly changing the requirements, precisely because nothing is built for posterity and there's tons of make-work churn. Good type systems make code far easier to refactor, and refactoring (as opposed to slapped-on new code) is the only way to handle shifting requirements without being crushed under ones own weight.
I'm not confident that average level developers are able to ship features in Rust as quickly as they would in Go, which is the root of my point. Those building tools, which generally do not have the same success metrics with respect to speed and correctness, should use the language with a focus on safety and correctness. Those whose positions do not lend themselves to safety and correctness should not use that tool.
Even if this was a genuine concern, they should still use Rust. Because it will be far easier to refactor the code that they ship into something that is safe and correct, compared to rewriting a Go codebase.
I don't write much Go code, but my company does. I have seen so many incidents and bugs whose root cause was: someone changed a library, that broke the semantics that users were relying on, but everything still compiled fine, so nobody noticed the subtly wrong behavior for a long time. An incredible amount of money has been lost like this.
Go simply does not give you the tools to prevent these issues in the type system, you have to rely on really thorough unit tests (which inevitably don't get written in the spirit of "moving fast".)
Whenever I hear about Rust in companies same dozen or so companies get mentioned every time.
But in general, companies adopt Go for the same reason they adopt MongoDB [0]: it's really easy to get started with, and get something that "works." The pain comes months or years down the road, and by then you're stuck with it.
[0] A company I previously worked for starting using MongoDB as a small startup, starting finding the limitations about 6 months later, but ending up spending an incredible amount of engineering time over 5 years getting rid of it.
We get it. You don't like Go. Don't use it. That's a perfectly fine option. Plenty of very successful companies, open source projects and services all work with Go (and literally every language) without issue. You not liking something does not make it bad.
As another example, Go makes it impossible to create a Maybe/Option type which leads to a bunch of issues around returning failing or empty values from functions. In one particularly costly example, there was a function in a library that was getting some price information from a file. Originally this returned nil when the price information could not be loaded, but a refactoring caused it instead to return 0 which the client happily used. This was not caught for _weeks_.
You can write unsafe code in Rust. Does that mean that Rust is bad too?
Hard to feel sympathetic, as this practice violates the Go convention of adding an additional return value to the function to indicate failure, either of type error or bool, as appropriate.
>Go makes it impossible to create a Maybe/Option type
It's very much possible: https://play.golang.org/p/MCxGcZ-rJRU.
Of course, it's not generic, but I have a feeling that might change soon :)
Go constantly requires boiler-plate checks for errors, null values etc. without the type checker helping ensure you've checked for an error or null value.
As for the second example I don't think it's a language issue but more a programmer one, how Rust would have saved you in that case, anyone could have returned 0 for the price instead of a proper type. Using Rust doesn't magically turn programmer into good ones. You still have to know how to properly design your code and best use the language and its features.
I'm often reading code in various language and I'm baffled at what a giant lib.rs looks like from someone that never really used Rust.
They wanted to do: something(getPrice()), but if getPrice can actually fail the then either something needs to accept an error, or they need to handle the error.
No type system imagined can save you from someone who's decided returning 0 is the correct way indicate an error in this scenario.
You've missed the problem that was posed. It wasn't returning 0 to indicate an error, it was changing the error value from nil to 0. In rust that would've been a type change (from Option<int> to int). Because the context here was about how stronger type systems (like rust's) allow you to be more specific about your types, and thus many code changes that would not involve the type changing in other more weakly-type languages do cause a type change in rust.
return 0, errors.New("unable to get price")
Go has its problems, and it isn't a perfect language, but I have never felt unproductive using it. In fact, my company uses it for all backend services. It has a great stdlib and first class tooling. Most of the discussion in this thread seems to be coming from people who barely use it or have only dabbled with go.
As a tangent, it's really tiring to see HN engage ad nauseum in these pointless language debates. Every language has its place; use it when it's appropriate.
The package ecosystem was so stable that go didn’t ship with a package manager (not saying it’s good but definitely a sign of relative stability).
Besides nil pointers (typesystem could do better here) and bad logic (can’t do better but language simplicity reduces this), what you’re saying is definitely not the experience of the majority. People constantly talk about being able to go to a golang program from 8 years ago and run it with no problems. Rust changes every few weeks.
You stated that "Rust is merging random syntaxes and random packages get upgraded to std lib all the time" as though it were incompatible with "being able to go to a program from 8 years ago and run it with no problems". But there's no incompatibility here. Rust adds new features at a faster rate than Go does, but it also maintains backwards compatibility ("stability without stagnation").
Sure the mainline stays clean but thats not what matters in practice.
Which also explains why you can git clone a Go library/tool and have it not building because some dependencies introduced some breaking changes in the master branch. That happened the last 3 times I wanted to fix something in a Go project.
I really don't know where this is coming from. The only package that was included into std like this is replacing the hashmap with hashbrown, and this didn't even change the public api of the standard library at all, besides improving performance of the hashmap.
In all likelihood, that "incredible amount" is a small fraction of the money your company saved in iteration velocity by not using Rust in the first place. This might not be true depending on your domain--if you're writing space shuttle software, bugs can be really expensive. If you're writing ordinary web app backend code, you're probably much better off with Go than Rust.
Not that Java is even good, but that beats go. The history of Go is the history of Java, repeated as farce. It's even some of the same academic lineage come to bail things out with the type system for generics!
Go is a dramatically nicer programming experience than Java. There are some benefits in Java however: sometimes JIT is nice and Go has no analog to Spring. But these are very circumstantial benefits and not good tradeoffs in the general case.
>No need to learn groovy to configure Gradle to build your application
I rarely have to configure msbuild, mostly to do some relatively advanced stuff like auto-installing npm dependencies for an SPA.
>No need to learn javadoc
Just use
/** */
You can build pseudo-statically linked executables by adding one line to .csproj (which builds a single executable file, but it's really a self-extracting archive), and real static linking is in the works. I have no need for it personally though.
>how to compile your code ahead of time
Same thing — AOT compilation is one configuration line away. You don't need it very much though, as the CLR is very performant these days and beats Go in most benchmarks:
https://benchmarksgame-team.pages.debian.net/benchmarksgame/...
>No need to figure out how to tune your GC for low latency and low memory usage
I would argue CLR's GC is ahead of Go's GC at least for latency. Memory usage, not so much, but damn, look at the execution times above. It depends on your priorities I guess.
>Plus Go has value types
C# has had them since before Go was a thing. Unlike Java, it also has real structs, which you can configure the alignment of, and map a raw chunk of memory to them (which you received from a COM port, for example). This came in handy more often than I care to remember.
As for your forest/banana analogy, I'd argue it's never been as bad in .NET world as it's been in Java world. I have personally never found anything similar to the insane class hierarchies they have in Spring.
Try to do something with stuff like XAML Workflows, Bizztalk, WCF, SharePoint, or MVVM. :)
Btw, did you know the default Gradle configuration for compiling a Java app is literally 1 line?
apply plugin: 'java'
Wrt gradle: While it’s super easy to get started, any slight modification is a major pain.
Note to other tooling guys for other languages:
- I don’t want to write in a new language just for my build system
- I don’t want freaking xml hell like maven
And don’t get me even started with Maven as a package manager. But to be honest... it’s at least better than NPM :-)
In general the concept of a "cross platform" build tool and "not having to learn another language" are at odds with each other, for anybody who isn't lucky enough to already work in the language the build tool is written in.
Those are the stapled languages in the backend space which Go competes in. You could give some of them a try.
I can easily see it being tedious if you have to type every character.
Code navigation is extremely basic (can only find references in the same package!), often breaks, and can't handle stuff like finding all interfaces that a type implements, or finding all implementations of an interface.
Then, I tried VSCode with the Go plugin, both the default version and the go pls based one; and Emacs with the LSP package and go pls.
Really good IDE support would include refactoring (more than renaming a local variable/struct field, e.g. Extract Function, extract parameter), advanced navigation/analysis (analyze data flow to/from variable, find call stack etc).
Go is somewhat decent in the tooling area, and you can get your job done with it, but it really doesn't have anything I would call good support in any area of tooling except the compiler (not code analysis, not debugging, not monitoring, not profiling, not package management).
I suppose it depends on what you're used to. I've never found myself wanting to do these things, but I'm also strictly from a Python and C++ background so my standards are admittedly lower than Java and C# people. Hopefully gopls solves for these problems.
2. There's lots of software that "ships" as a web service, often used by people who are not paying for the web service.
If you're talking about defects for an actual product that render it unsafe or unsuitable for the intended purpose, then I can see your point (though even there I'm not sure that I completely agree). But there's much more software than that.
As soon as I need to use someone else's code, all bets are off. Half the reason I want types is because it makes my life easier when I'm trying to use something written by someone else -- instead I find myself needing to experiment with a debugger to figure out what functions are actually doing.
Taking this gradual typing tool a step further, you can run your tests with the typeguard plugin for pytest, which will dynamically check the types of most values, pointing out places where your types are a lie.
https://typeguard.readthedocs.io/en/latest/userguide.html#us...
In my view, type checking lulls one into thinking the code is better than it actually is, just because it compiles. But it doesn't test the algorithms. And testing the algorithms exercises the code enough to reveal the shallow type errors.
But yes, there's a lull with type checking that makes people believe only negative testing is sufficient, which is as foolish as thinking only positive testing is sufficient.
What you point out is a developer error. Mixing variable types in a dynamically typed language is, like generics, a code smell.
Using a dynamically typed language is all about not having to babysit the compiler, its not about playing dumb about types.
If you design your functions in a way that that function will never receive an array, you dont have to test for it. And if some idiot tries one day, it should error very loudly that something is wrong.
Too many abuse dynamic typing to the point they feel safer offloading this headwork to a compiler.
That is, they get the compiler to make sure nobody will ever send an array into that function that takes a string.
All generics do is bring back the lack of typesafety and all the manual typechecking that comes with muddying generalizing the parameter typeset.
I actually dont hate generics, they are super powerful, but I question every usage as suspicious.
I also wish people would remember human brains arent all the same. We have different ways of thinking about problems. Some people need to have a compiler to busy work, some people need to do busy work while they think.
I just wish people shitting on dynamic typed languages would remember they came to solve the mess and monotomy that arose from typesafety.
Someone mentioned they felt go was going backwards from rust, i think both languages are massive steps backward from python.
Then you've moved it from a test to a runtime assertion. You're still re-implementing the type-checker, poorly.
A compile time error is a caught error. A run time error may be, or perhaps not.
A statically typed language with compile-time type checking would flag that immediately, and chances are your IDE will show the error before it even gets to that point.
Type hints are a thing, but then you are already moving in that direction while remaining in python.
A certain amount of it is probably a familiarity thing, but I do usually find myself able to parse it to the point of what line in which file things started to go wrong.
Besides that, i only said it was a code smell, i dont debate that its useful sometimes. Just that its a signal to be careful, check you really need itor there is t some other constraint you can break.
My only advice is that narrowing your parameter types at the earliest opportunity is a good practice and results in much easier to understand code.
But perhaps not enough.
"Convenience constructors" (i.e., static methods for creating instances from a set of parameters) are fine, but should often not be in the same module (or perhaps even the same package) as the class anyway. For example, if you have a Book class and it has a convenience constructor for creating a book from a database connection string and a book ID, this is probably reasonable for certain applications, but if it's likely that others would want to use your book class in non-database applications, then it would be a travesty to make the non-database application take a dependency on sqlalchemy, a database driver, etc (especially since database drivers tend to be C-extensions which may or may not be difficult to install on various target platforms).
I can assure you I do beleive they have their purpose and place in the world where raw performance or closer to metal abstractions can take place.
Personally, my brain much prefers to use a dynamic type system to infer what i mean leaving the thinking part up to me.
I just find defining a string is a string when im only ever going to put a string in there kind of redundant.
There are other arguments about readability, refactorability, and similar and I think they have some weight in large doverse systems with many many teams interacting.
Personally, that isnt a large issue for me. Im working at the scope I can maintain a standard and a level of consitency that alleviates these problems to the point the type safety is simply not wareanted from a return on investment point of view.
I do not, for instance, think the kernel or chrome should be rewritten in javascript. Despite what some react developers seem to think.
There are 2 problems with this kind of thinking.
1) you aren't going to be so sure. Humans are imperfect and as codebase grows, everyone commits such errors. Eg comparing a string to int without converting it to int in python. It always returns false (IIRC) and it is hard to detect where the problem is.
2) Most type systems aren't that verbose. I guess you got the impression from java / mediaeval C++. But most statically typed languages have local variable type inference. OCaml / Haskell / F# / Swift etc.. have varying degrees of type inference. At this point, types in method signatures, in languages that require it, serve as documentation. And many of these languages are terser than python/javascript.
1) I work on a typescript codebase for work. There is a real need for types in this case because the definitions are about 3 layers of abstraction away from their use. It drives me up the wall because I know when you keep definitions close to use, or have some basic conventions this problem melts away. At least to the point of diminishing returns where types are no longer relevant.
So, i guess over the years ive been caught out by int + string = 0 all of like, 1-2 times in production, maybe a few more while in dev. Either way its rare enough for me to call FUD on the argument. Stop mixing types and this really doesnt happen. To be fair to your point, at work, i know of a recurring error in production where this is almost certainly the same class of error. Nobody can be bothered fixing it because its too hard to track down and the cost benefit isnt there.
2) Type inference is problematic for me. Doesnt it just open you up to type errors of a different class?
2.5) terse code is not the point, I find rust cryptic and dense to say the least. I prefer something like go wgere readability is a priority over density.
It's at compile time, so not really? It will tell you exactly what it expects vs what you provided at compile time. These kind of languages read like dynamic languages (for the most part) but they are completely static.
I'm not sure if I'm misunderstanding you here, but generics are type safe. They're statically checked at compile-time.
That's naïve. Unless you code extra defensively (which is the same type of overhead as excessive testing, and needs itself to be verified by testing), there's very little guarantee that type errors will result in loud failure consistently at the first point that the bad value is passed (because functions that don't do unnecessary work often pass their arguments along without doing a lot of work dependent on the very specific type.)
And, in any case, failing consistently at compile time (or, with a modern code editor, at writing time) with static type checking is better than failing at runtime, even if it is loud and consistent.
Of course things like mypy and TypeScript (especially, in the latter case, because it powers tools that work pretty well when the actual immediate source is plain JS, or JS with JSDoc comments from which type information can be extracted, when consuming libraries with TS typings) mean that some popular dynamic languages have static type checking available with more expressive type systems than a number of popular statically-typed languages.
def foo(arg: str) -> int
def foo(arg: List[Union[Set[int],Optional[Dict[str, Any]]]]) -> str
Also, IIRC, better type inference.
It takes a while for something to settle down enough to say this version is going to be the code for the long run.
At that point, solidity in testing and gradual typing can be added, usually starting with the public interface.
Languages where I’ve had to satisfy all type errors in the various fragments of half brained code I’ve written for version 0.0.85 have always felt a little cumbersome. The compiler’s type checker is a perfectionist looking over my shoulder.
(Go is one of those languages. Ruby is not.)
Refactoring any dynamically typed application (regardless of size) is a manual operation, and error prone.
But then again I rarely deal with type errors, when I do it's the compiler looking out for my often 'application ending' mistakes.
Go, the language, is simple. Hard to argue with, and sounds great.
The code I have to write though, it's quite simpler to do it in Python more often than not.
What is missing is a language with good static type system (Algebraic data types, stream/iterators, generics), simple and having GC, for application domains where prototyping speed matters.
F#, OCaml and Haskell (and other ML-family languages) satisfy the first 3 criteria (type system, simple and GC) and depending on your familiarity with the language, can be fairly suitable for fast prototyping.
For example, I write most of my new personal projects in Haskell, and I'm able to iterate pretty rapidly once I have a skeleton of the system in place (with liberal use of typed holes to ignore things I don't care about implementing right now). For some projects, I find I'm actually able to prototype more rapidly than I would be able to in an untyped language, because the language helps me express the shape of the data through algebraic data types, and then the functions end up having "one obvious implementation" that follows the structure of the data.
OCaml is actually very good language. I hate how people outright dismiss it mentioning multicore. Neither JS nor Python have great multicore story. And most applications don't need multicore.
Wish there was a good static compilation toolchain for .net core. F# would gain much more traction then.
Mypy for Python (https://mypy.readthedocs.io/en/stable/) and Flow for Javascript (https://flow.org/en/docs/) are my personal favorites, and have all the features you describe. And importantly, both languages have very strong library support.
You need a for loop for what is done in other languages with one method call.
Removing an element from an array doesn't look like that. It is some slice appending trickery.
Having null and having to check errors every 5th line or so..
It lacks idioms like list comprehensions or map / filter. Reading code is spent in details like whether a for loop is index(), count(), map() or filter().
Instead of some simple code like x = condition ? a : b you are writing imperative verbose code like: if condition { x = a } else { x = b }
Go maybe simpler than enterprise-style java. But that's not 'simple'.
I must say I am biased, since I develop a language that I believe fits the sweet spot here. I would encourage you to give it a try: https://nim-lang.org
I think I get way more friction from:
- library authors that go crazy with generics.
- the million ways rust makes performance tradeoffs explicit (even when you're writing part of the program where performance simply doesn't matter).
- the million-and-one things you can do with an option type.
- the arcane macro syntax.
I could probably go on. I've been writing a lot of rust because I wanted a low-ish level language with good C interop, and I didn't want to learn C++, so I wasn't at any point a rust fanboy. I very much appreciate not having to be a genius to avoid segmentation faults, but other than that, I think rust is a somewhat ugly language - for the simple reason that it has a lot of features, some of which partially overlap, and most of which are vaguely inconsistent.
I'm probably sounding a bit harsher than I mean to - obviously, you can't expect a language like rust to have the simplicity and consistency of something like lua, and by and large, it's better than anything else I write programs in.
Still, the point is, as somebody with a lot of (fair and unfair) complaints, the burrow checker is not one of them. It complains rarely, and when it does you're almost always doing something stupid, unless you're doing something fairly arcane, in which case, you should probably use unsafe.
Rust effectively forces you to code like you're writing a multi-threaded app even when you aren't. There's a reason why people suck at writing multi-threaded apps: because it's hard. This is what people are fighting when they fight the borrow checker. And this is why so many people find it frustrating. There's all sorts of designs that flat out don't work or are way more effort than they're worth.
https://doc.rust-lang.org/book/ch04-02-references-and-borrow...
> At any given time, you can have either one mutable reference or any number of immutable references.
In practice, this is unworkable enough that it would basically forces you to reference count the Foo, so you could preserve pointers across calls by incrementing the reference count.
On the other hand, Rust's approach is suboptimal in cases where you're using reference counting anyway, or are willing to pay the cost of reference counting.
It just turns out that mathematically proving GC-free code to be free of use-after-free and double-free errors is really difficult unless you disallow a lot of things.
C also makes you think about ownership in your API design, it's just the language doesn't give you any real tools to express or enforce it. C++ gives you a bunch of tools and options, but you have to hope that you and the API you want to use agreed on which subset of the tools to use.
Garbage collected languages specifically take memory management out of the API design by declaring that the runtime will take care of it for everyone.
If you want lifetime to be something an API can control, then I think Rust's approach makes sense even though it obviously adds complexity. If you don't, then, yes, removing it from the equation definitely lowers the API design burden.
In many ways its analogous to having language support for strings. In C/C++, you gotta hope that the library you're using has the same approach to strings that you want (std::string? char*, wchar_t?, something else?). In newer languages, it's just a given. (For better or worse: because then you end up stuck with UTF-16 in some languages.)
That said I agree completely, `Option`/`Result` themselves (even if they are just intrinsic language elements, not user-implementable types) are valuable.
If you start talking about changing the recipe for Coca-Cola, surely Pepsi is going to enter the discussion at some point, right?
Fitting analogy: If there's an article about McDonald's, people would always talk about Wendy's instead. No one would mention BurgerKing (C++), Subway (D), KFC, ...
If any of these features is of significant value to a programming use case, it is worth talking about rust:
* Speed
* Type safety
* Memory safety
* Memory determinism
* Latency
* RAII-based resource acquisition and destruction
* Concurrency correctness / safety
* Minimal runtime requirements
* Low level bit manipulation (eg. Cryptography, compression)
* Startup time
* Networking
This isn't exhaustive, but it gives a lot of different people in different domains working on different problems a reason to talk about the same language when comparing to their usual choices.
That is context for discussion, and yes, it is relevant. Directly relevant, in fact.
I wanted to hear what Go devs have to say about this latest iteration of the generics proposal. But to do that I have to wade through endless comments about type systems and Rust. Even on comments directly talking about this iteration and how to use it, every other reply starts with "In Rust..."
If implementing generics leads more of the Rust community back to Go, then from what I've seen here: no thanks. I have a feeling we'd see every conversation in every community forum start with "In Rust.."
It's also a great discussion for the go community to have. The only problem here is that it's not a discussion you wanted to have. Should every discussion about go revolve around you and your wants?
If all you wanted was to hear what the go devs wanted to say, you could have clicked on the link and read it. Or could you possibly use the feature that was built for you: the [-] button to collapse a thread. Or maybe, just maybe, you could go to a place that is explicitly only about go, like /r/golang.
But it's every freaking time. Every single time Go is mentioned, there's a ton of Rust folk commenting on how Rust does it (better).
Just for once, it'd be nice to have a comment thread discussing a Go-specific item, that has nothing to do with Rust, without talking about Rust.
And yeah, /r/golang is at least Go-focused. But it has its own problems too. Mostly PHP and JS folks learning Go and asking basic questions (which would be great if they didn't then reply to the answers with "but that's not how PHP/JS does it, why does Go do it so strangely?" and without reading any of the billion answers for that question already).
Sorry if my exasperation is showing ;)
The only cases I know of are people moved to Rust to avoid GC pauses.
PHP must be Taco Bell. It solves a lot of problems quickly, but you'll pay for it later.
I’ve been a long-time user of Haskell, but I can safely say Rust has supplanted it almost entirely for me at this point. I never would have felt comfortable betting on Haskell in a commercial environment. Rust? Absolutely.
I chose my analogy carefully. Coca-Cola tried to change its recipe to make it sweeter because they did studies and found people liked the taste of Pepsi more. So any discussion of changing Coke's flavor means Pepsi is highly relevant. But the converse is not necessarily true. Pepsi doesn't have any (recent) history of trying to match their flavor to Coke.
Maybe a better analogy is this: if Mercedes comes out with an electric car, you should expect to see Tesla in the discussions. But if Tesla comes out with a combustion engine, there's nothing particularly relevant about Mercedes in that discussion.
I'm sure that if there were discussions about adding structural typing or lightweight fibers to Rust, then Go would show up. But most of the discussions tend to be around adding generics or sum types to Go.
The HN comments on this article have been derailed from any interesting discussion about Generics in Go to an utterly pointless religious war about Rust and type systems.
1. This opinion gets expressed on every single comment thread about Go, multiple times. Maybe have some respect for other people's right to have a discussion on a subject without derailing it with a tangential opinion about another language.
2. We all know that Rust is the one true programming language for every possible context. However, because we're clearly idiots, we're writing a program in Go. Pointing out how Rust would do it better isn't helping.
> a style of computer programming characterized by the _ritual_ inclusion of code or program structures that serve no real purpose.
Today Rust and Go exist in different spaces. Go is a Python/Ruby/Java/etc alternative. Whereas Rust is an alternative to C/C++/etc. Obviously there is overlap between those sets of languages but that doesn't really mean Rust and Go are as directly comparable as HN comments might lead people to believe.
I don't understand people trying to make "a language that does it all". There has been a lot of that in Go, in Rust, in JavaScript, in Java, in TypeScript, in C++, in Haskell, in D...
Except that in this years Rust survey, there were more people using Rust for "Backend Development" than any other purpose. Rust allows you low-level control, but in many ways it's higher-level than Go (it allows for more sophisticated abstractions that can be wrapped up in libraries). It's an excellent choice for web services. And many people find it more productive than Go (although the reverse is also true).
You make it sound as if Python/Ruby/Java on one hand and C/C++ on the other are two well established, well delineated language blocks with completely different uses cases. That's never been the case in my experience, especially with the pair Java vs. C++ which might be the most apt comparison for Go vs. Rust.
It's absolutely obvious to me that Go and Rust are competing for market share, there's no reason why ripgrep couldn't be written in Go or fzf in Rust for instance.
Maybe it's irrelevant and there's enough room for both languages to coexist and thrive in the long term, but in my experience they really don't exist in different spaces at all.
In terms of “feeling”, Go feels like a polished form of C to me. Rust doesn’t feel like C++ to me — it actually feels much more like OCaml and even Haskell. Though Haskel no doubt has a more sophisticated type system, I still find that a shocking number of design practices that I used in Haskell port naturally to Rust.
To me, Go vs JVM ecosystem languages is a much more difficult choice. I would have to actually think a bit.
To me, Rust and Go really don't occupy the same ecosystem niche. I can't think of a project where I would have to choose between them--the choice between them is almost always dead obvious given the project description.
Edit: last I looked you could see how many OS threads would be used by looking at runtime.GOMAXPROCS. There was a time when it would just default to 1, but it looks like they changed it. When I last programmed in Go you had to override it via an environment variable or set it in code.
Whereas Rust user and committers are much more interested in discussing what is good programming, nuances of PL theory and so on. It does not matter if the post is about Rust or not and specially if it is about Go.
As for programming with types, that's partly what Go was trying to avoid: https://news.ycombinator.com/item?id=6821389 . And I agree with Pike on this one. The nice thing about Go for me is that I'm just writing code. Not defining a type hierarchy, not rewriting some things to get them just right, not defining getters, setters, move and copy constructors for every type :). Just telling the computer what to do and in what order. When I'm writing a library I'm defining an API, but that's about it; and you can usually steal whatever the standard library's patterns are there.
I disagree about nil as well; I think Go's zero value approach is useful, and basically impossible without nil (it wasn't necessary in my code, but I may want to instantiate an ApiResponse object without a data structure ready to be passed in).
A little bit of a rambly response from me, but, all in all, I think I'll be one of the stubborn ones which refuses to use generics in his code for a long time.
I like your solution to my imaginary problem, but I am going to counter this one. Now I'm salty because nil interface[1] actually bit me once and cost me. Go's zero value approach also exists in Rust, but is type safe. Basically every primitive type, and Option<T> have zero values. Any struct that is made up of those values can also safely have zero values. Then for those that don't, you can implement your own zero values. This is called Default in Rust. Go's zero value approach is perfectly possible, and arguable better without nil. And even then, the number of times I've seen a service crash because someone "forgot" to initialize a nullable type, and passed it to a function that then exploded isn't an issue I should deal with in 2020.
[1] https://medium.com/@glucn/golang-an-interface-holding-a-nil-...
As for your proposal, there are some issues with it: not all structures have a sane default for all not optional, nilable parameters. What is the default underlying reader for a bufio.Reader? A reader which returns zero bytes? Certainly that would be more confusing to debug than a simple panic, which is what we have now [2]. There's also the fact that a zero value is just a value with all the bytes zeroed and allocating an object via language means (new) never allocates more than the size of the object and doesn't do computation.
But I guess the main point would be that I simply do not have a problem programming with nil-able types. Failing to initialize in Go means writing var a *T as opposed to a := &T{} or a := NewT(), which seems like an odd mistake to make - or forgetting to initialize a member of a struct in the NewT() function. Fundamentally, I do not want to spend hours of my life dealing with safeguards which are protecting me from a few minutes of debugging.
But hey, that's just me. Go isn't Rust and Rust isn't Go and that's a good thing.
[1]: https://play.golang.org/p/L7iy9YBC55c [2]: https://play.golang.org/p/Vgv73KhegKI
I think you're actually agreeing with nemothekid here, what you're saying is that there is no sensible default value for a bufio.Reader. In Rust terminology, that would mean bufio.Reader would not implement the Default trait. Types need to explicitly implement the Default trait, so only types where that makes sense implement it.
> I simply do not have a problem programming with nil-able types
Yes, that's going to make a big difference to how you feel about features that reduce the chance of errors like that. I'd hazard a guess that in C# the most common exception that is thrown is the NullReferenceException, after a quick search[1] it looks like NullPointerException is a good bet for the most common exception in Java. Most of those IlligalArgumentExceptions are probably from null checks too.
> Fundamentally, I do not want to spend hours of my life dealing with safeguards which are protecting me from a few minutes of debugging.
Similarly, I've already spent hours of my live dealing with null and undefined value errors, and I'd like to stop doing that. So I welcome new languages and new language features that help to stop those errors before they happen.
[1] https://blog.overops.com/the-top-10-exceptions-types-in-prod...
> Sounds like Rob Pike doesn't understand type theory.
I'd be a bit more charitable; Pike is a smart dude, I'm sure he does understand type theory, but has decided he'd prefer to write imperative code. And he's actually good at writing imperative code correctly, so for him, that works. But most people are not very good at writing imperative code correctly, at least not the first time, and not without writing a large volume of tests (usually several times as much test code as program code) to verify that imperative code.
Or perhaps Pike was just assuming the person he was talking to was only talking about types in the OOP sense. If that's the case, I agree with him: taxonomies are boring, and inheritance often leads to leaky abstractions.
But types let you do so much more than that. I much prefer being able to encode behavior and constraints into the types I define over writing a bunch of tests to verify that the constraints I've expressed in code are correct. Why do the work that a compiler can do for you, and do it much better and more reliably than you?
How are languages other than Go (like Rust, Swift etc.,) not imperative? They are nearly as much imperative as Go but have FP features like ADTs and pattern matching, but those don't make them "functional". This point might be valid if you are talking about Haskell, MLs and the likes.
> I much prefer being able to encode behavior and constraints > into the types I define over writing a bunch of tests to verify that the constraints > I've expressed in code are correct. Why do the work that a compiler can > do for you, and do it much better and more reliably than you?
IMO, this "types replacing tests" might be true when comparing dynamic vs static typing, but for already static typed languages, extra typing cannot be a substantial gain. Personally, I find type-level programming beyond a certain extent to be counter productive and it doesn't seem to have much impact on correctness (unless we bring in dependent types).
I just fundamentally disagree that "extra typing" (as you put it) doesn't give you much of a gain in correctness confidence.
The best example of this which I have seen is Amos' https://fasterthanli.me/blog/2020/i-want-off-mr-golangs-wild... in which he chastises Go for allowing him to print filenames which contain non-UTF-8 data to the terminal which does not display correctly, instead of forcing them be escaped. Rust does that, so he is confident that the program he writes in Rust handles filenames properly: if they are UTF-8 they are printed normally, if they are not they are escaped. Since the Rust type system allows him to do this, it must be correct, right? Of course not. Filenames which contain vt100 escape codes would do a lot more damage and they are not handled at all.
At the end of the day you still have to think of all the possible cases. Types help to constrain the number of possible cases, but the more time you're spending making type constraints as narrow as possible, the less time you're spending handling the cases which can never be caught by the type system.
By the way, generics are not at all exclusive to FP. Both C++ and D proved advanced generic/meta-programming facilities like template template parameters(HKTs) and constant generics which Rust currently lacks. But I'd certainly not use these if there is no absolute need.
What I objected to was abstracting and generalizing too much to the point of over-engineering. Some type systems, like those of Rust and Haskell, provide more room for such abuse and it takes some discipline to keep it simple. In contrast, OCaml is a very good sweet spot. ML modules are as powerful as type classes and lead to much cleaner and simpler APIs. OCaml compiles even faster than Go!
It's designed to be simple, to be boilerplate, to be easily reviewable/checkable by coding teams.
Not sure why Go and Rust are always the compared languages. Go is designed to replace Java/RoR/Python in Enterprise-land, not to replace C/C++.
Rust is designed to replace C/C++ in system-land, embedded, kernel, thick app components (browsers are probably the most complex apps running these days on end user systems). The entire focus is zero-cost abstractions.
Rust can't cover the enterprise use-cases of Go the same way that Go won't ever cover what Rust can do on systems/embedded level but there is enough overlap in some cases to confuse people into trying to compare them directly.
Secondly, I don't think the fact that Go making the opposite trade-offs in terms of (let's say) programmer effort vs. CPU clock cycles means it is a "language for the average". Go is great for any number of interesting high-level server-side components where it being done in half the time is better than it being 15% faster.
> We—Ken, Robert and myself—were C++ programmers when we designed a new language to solve the problems that we thought needed to be solved for the kind of software we wrote. It seems almost paradoxical that other C++ programmers don't seem to care.
https://commandcenter.blogspot.com/2012/06/less-is-exponenti...
I have seen average programmers who can write less dumbed down code than the most succinct code possible in Go.
I have seen below average programmers who understand how to use generic data structures / programs in C++ / Java / C# etc..
> It's designed to be simple, to be boilerplate, to be easily reviewable/checkable by coding teams.
Boilerplate and easily reviewable are at the odds. Unless Enterprise style java is the bar, it is hard for anyone to say that. Go is too much boilerplate than average programmer's python code, for example. Don't tell me python is dynamic. The average programmer doesn't do metaclass magic.
Being so much boilerplate and verbose `if err != nil` and no generics and no methods/functions for common operations like finding the index of an element in an array. All this leads to for-loop-inside-while-loop-inside-for-loop attrocities where it is harder to decipher what the intention is. Compare to python where you have methods on collections to carry out common manipulations, and list comprehension in python is so cleaner than 4 line imperative go code.
Go seems to miss why python/JS/ruby are so popular. It is because so much is built in that you can communicate __intent__ clearly without getting bogged down in details. Compared to any modern language that's not C and not mediaeval C++, Go is so much more verbose. Even java has enough shortcuts to do these common things.
And don't start telling me this leads to incomprehensible code. Coding standards are there. What's unreadable is 8 level indented imperative attrocity of blue collar language Go.
> Not sure why Go and Rust are always the compared languages.
They both emerged at same time and have some overlapping scope - eg static native compilation, memory safety etc.. but there similarities end. However, there is lack of a a popular, succinct natively compiled language which gets out of the way to write software. Everyone knows expressive languages need not be slow or difficult to deploy. Some people have to write Go in dayjob and the sibling rust, having quality-of-life improvements that anyone expects in a post-2000 language [0], seems to be a closer candidate to comparison (even though rust isn't the optimal language for the things Go is used for, given it is a systems language with static memory management) Others like D and Nim have a fraction of users. Of course there are also some vocal rust fanboys who think crab god is not popular because world is anti intellectual.
> Go seems to miss why python/JS/ruby are so popular.
Not sure what is there to miss especially since Go is pretty popular for its age. Considering it is not even mandated or officially supported like Swift by Apple, or Dart/Kotlin by Google/Android.
> to be easily reviewable/checkable by coding teams.
I strongly disagree with this. I find Go code to be incredibly difficult to read. This is because of two main reasons.
The first is that the lack of expressive power in the language means that many simple algorithms get inlined into the code instead of using an abstraction with a simple and understandable name. I find that the first pass of the code is me reading over the lines (each of which is very simple and understandable) and virtually abstracting it into what the code actually does. I find that the interesting business logic is lost in all of the boilerplate.
out := []int{}
for _, v := range input {
number, err := fetchData(v)
if err != nil {
return nil, err
}
if math.Abs(float64(number)) <= 2 {
continue
}
out = append(out, v)
}
return out
input.iter()
.map(|&v| fetch(v))
.filter_ok(|number| number.abs() > 2)
.collect()
Secondly the "defaults are useful" idea is in my opinion the worst mistake the language made. They repeated The Billion Dollar Mistake from C. I have seen multiple expensive production issues as a result of it and it makes code review much harder because you need to check that something wasn't uninitialized or nil. It is absolutely amazing in Rust that I don't have to worry about this for most types (depends on your exact coding style, in the above example there is never a variable that isn't "complete").
So while Go may be quick to write. I think the understandably is deceiving. Yes, I can understand every line, but understanding the program/patch as a whole becomes much more difficult because of the lack of abstraction. Humans can only hold so much in our head, making abstraction a critical tool for understandable code. So while too much of the medicine can be worse that the disease I think Go aimed - and hit - far, far below the ideal abstraction level.
I think this is the fundamental point of contention. Go aims at abstraction at the package level. Each package exports a set of types and functions which are "magic" to outsiders and can be used by outsiders - an API, if you will. Rust seems to aim at abstraction at the line level - each line is an abstract "magic" representation of what it is meant to do.
In your Go code, the only pieces of line-level magic are `range` and arguably `append` (even though I would argue it is integral to the concept of slices). And of course the API magic of `fetchData` and `abs` which is in both versions.
On the other hand, Rust has .iter(), .map(), .filter_ok() and .collect(). So, while I think anyone could understand the Go code if you explained `range` to them, I do not understand the Rust code. Yes, I understand what it does, but I have no clue how it does it. What is the type of .iter()? Why can I map over it? Why can I filter a map?
But that's not the point of the Rust code. The Rust code expresses what should be done, not how it is to be done.
The way Rust deals with complexity is by offering tools which push that complexity into the type system, so you do not have to keep everything in your head. The way Go deals with complexity is by eliminating it and, when that is not possible, by making sure it does not cross API boundaries. In Go you do keep everything in your head.
That's a Go feature.
> I think this is the fundamental point of contention.
I agree with your point. Part of Go was definitely the removal of unnecessary abstraction and complication. However my argument is that they went too far.
> Go aims at abstraction at the package level [...] Rust seems to aim at abstraction at the line level
I don't understand the difference in your mind vs package level or line level. For whatever is exposed as a package is surely intended to be used in a line elsewhere in the program.
> On the other hand, Rust has .iter(), .map(), .filter_ok() and .collect(). So, while I think anyone could understand the Go code if you explained `range` to them
If you explain range, continue, return and append then you could understand the Go snippet. I don't see how this is meaningfully different from explaining iter, map, filter_ok and collect. Sure, the former are language features while the latter are library features but that doesn't seem to be a meaningful difference when it comes to comprehension.
> Yes, I understand what it does, but I have no clue how it does it.
This is the whole point of my argument. You don't need to understand how it works. Much like you don't need to understand how continue or append work in go. That is the point of abstraction. You need to know what they do, not how they do it. In my opinion Go forces you to leave too much of this usually-irrelevant plumbing in the code, which distracts from the interesting bits.
> The way Go deals with complexity is by eliminating it
This is again my key point. I'm arguing that in most cases Go hasn't managed to eliminate the complexity. Maybe it got rid of a little, as your "map" loop doesn't need to be as generic and perfect as the Iterator::map in the standard library. But the complexity that is left is now scattered around your codebase, instead of organized and maintained in the standard library.
The intrinsic complexity has to live somewhere. And in Go I find a lot more lives inline in your code. In other languages I find it is much easier to move the repetitive, boilerplate elsewhere. And when this is done well, it makes the code much, much easier to read and modify as well as leading to more correct code on average.
> That's a Go feature.
I agree with that. But what I am trying to express that in my experience this is actually a flaw. It looks good at the beginning. But once you start reviewing code you start to see it break down. I think Go had a great idea, but based on my experience I don't think it worked out.
Absolutely. The difference is that Go has a limited number of such features and once you have learnt them that's all you need to know, in that sense, and can understand any code base.
One thing which I have not expressed very well in my reply is what exactly I meant by "understanding what the code does". When you look at func fetchData(T1) (T2, error), it's easy to understand what it does: it fetches some data from T1 and returns it as T2, with the possibility of it failing, and returning an error. If you know what T1 and T2 are (which you should if you're inspecting that code), that's usually sufficient. You understand (almost) all of it's observable behavior, which is different from it's implementation details. Similarly, `abs` returns the absolute value of a number
`append` also has easy to understand observable behavior: it appends the elements starting at position len(slice) and reallocating it if necessary (generally, if the capacity is not big enough), but it's actual implementation is undoubtedly very complex. `range` is harder to explain, but rather intuitive when you get the hang of it.
Of course you also want to keep in mind the behavior of all the language primitives as well: operators, control flow etc. In Go, you have to keep all of these things in your head to understand what is happening in the code, but once you do you really understand it.
We can call all of these things: variables, language primitives, API functions etc. atoms of behavior. In Go, to understand a piece of code, you first have to understand what the observable behavior (but usually not the implementation) of all of the atoms in that code are, and then understand all of the interactions between those atoms that happen as a result of programmer instructions.
What I mean by line-level vs package-level abstraction is quite simple (maybe not the best names, but hey, I'll stick with them). With package-level abstraction, the atoms, as well as the interactions between them, remain conceptually easy to understand, but become more powerful as you move up the import tree. The observable behavior of an HTTPS GET is easy to understand, but very complex under the hood.
With line-level abstractions the atoms, and especially the interactions between them, become very complex. The programmer no longer "has to understand" the observable behavior of every single function he uses. Odd one-off mutators are preferred to inlining the mutation because it "makes the code more expressive" - in that it makes it look more like english, it makes it easier to understand what the programmer is trying to do. It does not, however, make it easier to understand what the programmer is actually doing, because the number of atoms - and their complexity - increases substantially. If you want to get a feel for this look at the explanation for any complex feature in C++ on cppreference.com. I must have read the page on rvalue references 20 times by now and I still don't grok it.
Of course, with line-level abstraction, the programmer doesn't need to constantly keep in mind 100% of the behavior of the atoms he's using, much less whoever's reading.
I can't tell you which one's better - probably both have their place - all I'm saying is that I, personally, can't work with C++/Rust/other languages in that style. I've tried to use them but I can't. C is easier to use - for me.
Paragraphs 2 through 6 seem like they would apply to most, if not all, languages, even if the language is more complex. For example, here's the text with a few minor alterations:
> One thing which I have not expressed very well in my reply is what exactly I meant by "understanding what the code does". When you look at `fn fetch_data(input: T1) -> Result<T2, Error>`, it's easy to understand what it does: it fetches some data from T1 and returns it as T2, with the possibility of it failing, and returning an error. If you know what T1 and T2 are (which you should if you're inspecting that code), that's usually sufficient. You understand (almost) all of it's observable behavior, which is different from it's implementation details. Similarly, `abs` returns the absolute value of a number
> `Vec::push` also has easy to understand observable behavior: it appends the elements starting at position vec.len() and reallocating it if necessary (generally, if the capacity is not big enough), but it's actual implementation is undoubtedly very complex. `Vec::iter` is harder to explain, but rather intuitive when you get the hang of it.
> Of course you also want to keep in mind the behavior of all the language primitives as well: operators, control flow etc. In Rust, you have to keep all of these things in your head to understand what is happening in the code, but once you do you really understand it.
> We can call all of these things: variables, language primitives, API functions etc. atoms of behavior. In Rust, to understand a piece of code, you first have to understand what the observable behavior (but usually not the implementation) of all of the atoms in that code are, and then understand all of the interactions between those atoms that happen as a result of programmer instructions.
The details differ, but the overall points remain true, do they not?
Unfortunately, I'm still confused after your description of line-level vs. package-level abstraction. Just to make sure I'm understanding you correctly, you say an HTTPS GET is an example of a package-level abstraction, and an "odd one-off mutator" (presumably referring to a functional/stream-style thing like map()/filter()) is an example of a line-level abstraction?
If so, I'm afraid to say that I fail to see the distinction in terms of package-level vs. line-level abstraction, since what you said could apply equally well to both HTTPS GET and map()/filter(). For example, if a programmer uses a function for an HTTPS GET instead of inlining the function's implementation, you can say "using the function is preferred to inlining the request because it 'makes the code more expressive' --- in that it makes it look more like English, it makes it easier to understand what the programmer is trying to do. It does not, however, make it easier to understand what the programmer is actually doing..."
That's the nature of abstractions. You hide away how something is done in favor of what is being done.
> With line-level abstractions the atoms, and especially the interactions between them, become very complex. The programmer no longer "has to understand" the observable behavior of every single function he uses.
I believe your second sentence here is wrong. Of course the programmer needs to understand the observable behavior of the functions being used --- how else would they be sure that what they are writing is correct?
> Odd one-off mutators are preferred to inlining the mutation because it "makes the code more expressive"
I think you might misunderstand the purpose of functions like map() and filter() if you call them "odd one-off mutators". The same way that `httpsGet` might package the concept of executing an HTTPS GET request, map() and filter() package the concept of perform-operation-on-each-item-of-stream and select-stream-of-elements-matching-criteria.
> If you want to get a feel for this look at the explanation for any complex feature in C++ on cppreference.com. I must have read the page on rvalue references 20 times by now and I still don't grok it.
You need to be careful here; in this case, I don't think rvalue references are a great example because those aren't really meant to abstract away behavior; on the contrary, they introduce new behavior/state that did not exist before. It makes sense, then, that they add complexity.
In the end, to me it feels like "package-level" and "line-level" abstractions are two sides of the same coin. The functions exposed by a "package-level abstraction" become a "line-level abstraction" when used by a programmer in a different part of the code.
I think this is an excellent point. I have Go code which might make Rust fan apoplectic with its verbosity and basicness. But for me it is like magic every time it runs and get stuff done on any of my remote/local machine.
I made a similar point elsewhere about expression verbosity vs project verbosity. To me all the 3rd party dependencies, substantial number of outside tools and obscure setup files are a type of verbosity when I work on a project. Though I do not mind them if thats what is needed.
Are line-level vs. package-level abstractions are necessarily mutually exclusive? One could argue that the functions Rust iterators expose are "'magic' to outsiders and can be used by outsiders --- an API, if you will".
> but I have no clue how it does it
The question here is whether it actually matters whether you know how the Rust code works. You don't necessarily need to know how `range` or `append` work; you just need to know what they do. Why should the Rust code be held to a different standard in this case?
If I understand it correctly, your code doesn't check when unmarshalling if the content of Data has the expected structure. Using interface{} it's always been possible to achieve something like you'd do with Generics but it's ugly and can't check types at compile time.
> The jury is out if thats is a good thing or a bad thing
Well said. I have this same thought with TypeScript on a frequent basis.
The way I look at it, and I could totally be wrong, is if you go for a different language for your back-end than your front-end, it betters pay off big time. I find Go and Typescript to be in a very similar ballpark in term of productivity, but with Typescript having a huge advantage since you can reuse all the learning/tooling from the front-end.
Rust on the other hand really adds something to the table with the memory safety and zero-cost abstraction.
TL&DR: It feels like either you eat the bullet and go Rust for memory safety, or Typescript is a better choice. Of course I'm overly simplifying.
Thoughts?
Go shines when you have a lot of parallelism, and not a lot of concurrency (although sync package is fantastic). Web servers, data processing pipes, task queue consumers...
Also the language is simpler. Personally I think in it like C vs C++ or RISC vs CISC.
And last, but not least: Go have faster compilation times. Rust compilation is slow, and for some tasks that requires retrying (like learning a new language) compiling fast is very valuable.
For the majority of software (I guess you are referring to web apps), simpler/GC/scripting languages like TypeScript or Go are better.
But, if you really need something low-level, then you need C, C++, Rust, Zig, etc. and there is no way around it.
So is Haskell. What I'm saying is that in 2020 the dev workflow is not: code, compile, run, repeat. Thanks to modern tooling it is now a near-instant feedback loop of: code, red wiggly line(s), fix, repeat. Ie. real-time conversation with the compiler.
What does get rid of errors is IDE support for nullable types which warns the programmer that they have accessed a property without checking for nulls. Take kotlin and Intellij/IDEA for instance.
IDE support is half baked, someone can always turn it off.
(Probably mangled the Swift, doing this from memory)
The way I tend to look at this is the 30 minutes I spend up front making my types work will usually save me hours of time later (sometimes much later, and spread over different coding sessions), because if I'm using the type system to enforce constraints, I'm not going to have to worry about writing buggy constraint code.
When I was learning Scala (after working in Java most of the time), I noticed that I would sometimes spend quite a bit of time getting short snippets of code correct so the types would line up. The result would be shorter than the equivalent Java code. But I had much more confidence in that code actually working, without needing to write tests (or at least as many tests), because I was leaning hard on the type system to prove the code correct. You can do that to some extent in Java, but the type system there is a bit weaker, and the standard library and common idioms make it harder to do. Ultimately if I have a chunk of Java code and a chunk of Scala code that does the same thing, I'm much more confident in the Scala code because I know scalac is providing me stronger guarantees than javac, assuming I've written the code to make good use of the compiler's abilities.
My vote goes towards good thing.
One of the things I like most about Rust is that it forces you to think through your design and address complex tradeoffs, and often won't even compile until you do.
What it costs you in development time, you'll make back in reduced maintenance. The former is a visible cost therefore you feel it more than the latter which is invisible when things run well.
This is why Rust can feel less productive even if it makes you more productive in the long term if you take in to account less maintenance.
I wouldn't want to spend that time one a one off script I only expect to run a few times.
I also wouldn't want to spend that time only to find that my assumptions were wrong or the requirements changed and I have to throw it all away for a new class puzzle.
You don't have to. No generics, `.clone()` and `.unwrap()` everywhere, and the Rust code goes brrrrr. :D
Recently started getting into Xonsh cause it still makes piping programs super easy, while being still fairly easy to provision.
Really wish there were a (stable) go-based scripting language and shell. There's tengo and some other things, but not primetime ready.
I have heard this bullshit enough times. "Orange crab god doesn't like it so you are doing it wrong". No, you shouldn't have to care about memory management nuisances when that's not relevant and rust being a language suited for systems domains with correct static memory management (Good thing for systems domain), makes those irrelevant details surface in implementation.. what you said isn't true for other domains.
This kind of shilling is what leads to rust evangelism strike force memes.
In C++ you can write:
template <typename Animal>
void roar(Animal animal) { ... }
roar(airplane); // How do Airplanes roar?
roar(truck); // Trucks can roar... but roar expected Animal
fn roar(animal: impl Animal);
That's a good thing, but maybe somebody did wanted to call roar with a truck, and now you have to invest time into more precisely thinking which types should roar actually take, which types constraints make sense defining, how you categorize types, etc.
In Rust thinking about these things costs time. In C++ it also costs time, usually more than Rust, because you have to go way out of your way to prevent mistakes like the above. In Go you don't have to think about these issues at all because the language does not allow you to do most of this (except for interfaces, but that's another story).
What irritates me is claims like "If borrow checker rejects your code, it was wrongly structured anyway" and "rust's restrictions lead to good structured code". It is not wrong if program logic requires self referential structures, for example. Neither does it make sense to evangelize rust using blanket statements like this. I get the impression that some people are trying to evangelize rust as a language for everything.
The mental overhead of rust (or maybe ATS, maybe Ada/SPARK, depending on requirements) makes sense for systems programming, where C/C++ will make stuff even more complicated, and you can't compromise on performance. The applications domain is realistically better served by something like F# / OCaml / Go once it gets generics..
Nobody is claiming that? At least not in this thread.
I think your confusion stems for thinking that "Rust == borrow checker". The borrow checker is a tiny part of Rust.
> The mental overhead of rust
I find the mental overhead of Rust to be smaller than that of Python, Go, Java, Haskell, C, C++, Lisp, and pretty much any other language that I've ever used.
In Rust I don't have to think about multi-threading, data-races, memory management, resource acquisition and release... the compiler does the thinking for me. I also can refactor and reshuffle code at will, and trust the compiler to catch all errors.
Changing a type that pretty much every translation uses in a 500k LOC code base and add multi-threading to it? No problem, just try it out, and if it compiles, it is correct.
I can't say the same of Go, Python, Java, etc. where threading errors are impossible to debug. And well, it wouldn't even be worth trying. It would be impossible to make sure that the code is correct, even after fuzzing for weeks.
I usually do stuff like this as a YAGNI exercise. Don't spend the extra 25 minutes thinking about it until you know you have 3 or so cases where you'd actually be sharing code. But at that point... the consistency you can get starts to become attractive, if you want the behavior to stay consistent in the future!
It includes:
- Having some understanding of how type systems tend to work and common patterns around them, preferable in a abstrac non language specific way. Do not confuse it with knowing formal CS since type theories, it's not the same.
- Knowing how to effectively use the type system to encode important variants.
But probably even more important:
- Not getting obsessed with trying "perfectly"/"optimally" use the type system.
- Knowing that the moment your types and their relations get too complex it might not be worth it at all, even if you encode use-full variants. Sometimes just having runtime checks is so much better from a API UX point of view. Getting complex type system based API's right is hard and from what I see in the open source community most people do not have the skill to do it right. (Through this doesn't mean not using the type system to encoded constraints, just not over using it!). A common case where this happens is when people try to use the type system to force a DSL into a language which isn't very compatible with that kind of DSL.
While I often see people learning about how they can use advanced features of a type system but they do not learn when to _not_ use it.
Disclaimer: I just realized that what I see as Simple usage of the type system the parent post might already see as advanced usage.
This is very real. One reason I like Rust for serious projects that deserve this level of thinking time, but I'm wary to use it for simple 'toys'. Go was far easier to jump into but also far easier to push against its limits.
Some sort of compromise might seem better here but I like using the best language for the job. Rather than some all-encompassing developer experience or language use-cases.
I think you summarize it perfectly though, my favorite parts of Rust are Option/Result.
I find it much easier on the eyes than java.
Unfortunately, I have had to deal with too much "exciting" code. So I am very happy with Go so far and this latest concept of generics seems to add the least amount of complexity for the problems it solves.
i feel like i'm at a point of language overload as it is these days, I don't have the mental space for yet another language
I agree with you that I think they're slow to improve. I'm not sure if innovation is necessary though, since most people rely on the language being stable going forward.
Personally I struggle with deciding when to use Go for a new project. With so many languages now supporting different concurrency paradigms, and containers abstracting away prior deployment pain points, I'm not sure why I'd reach for Go over any of the others.
I'm pleased to see they've made this proposal even more boring and removed contracts.