Hacker News Reader

Comment by Jtsummers | Hacker News Reader

In the statement/expression-oriented axis of languages, Go is a statement oriented language (like C, Pascal, Ada, lots of others). This is in contrast to expression oriented languages like the Lisp family, most, if not all, functional languages, Ruby, Smalltalk and some others.

Expressions produce a value, statements do not. That's the key distinction. In C, if statements do not produce a value. In Lisp, if expressions do. This changes where the expression/statement is able to be used and, consequently, how you might construct programs.

View on HN

A simple example for anyone who might not appreciate why this can be so nice.

In languages where if is a statement (aka returns no value), you'd write code like

int value;

if(condition) { value = 5; } else { value = 10; }

Instead of just int value = if(condition) {5} else {10}

Some languages leave ifs as statements but add trinary as a way to get the same effect which is an acceptable workaround, but at least for me there are times I appreciate an if statement because it stands out more making it obvious what I'm doing.

How would this work if I need to update multiple variables?

  int value1 = 0;
  int value2 = 0;
  if (condition) {
    value1 = 8;
    value2 = 16;
  } else {
    value1 = 128;
    value2 = 256;
  }

Would I have to repeat the if expression twice?

  int value1 = if (condition) { 8 } else { 128 };
  int value2 = if (condition) { 16 } else { 256 };

Depends on the language a bit, but a common feature in these languages is the tuple. Using a tuple you would end up with something like:

let (value1, value2) = if (condition) { (8, 16) } else { (16, 256) }

Or else you’d just use some other sort of compound value like a struct or something. Tuple is just convenient for doing it on the fly.

hah we gave basically the same example on the same minute.

I love destructuring so much, I don't know if I'd want to use a language without it anymore.

It’s actually so painful to go back to languages without destructuring and pattern matching.

As someone who writes a fair bit of c# making switch and if's into expressions and adding Discriminated Unions (which they are actually working on) are my biggest "please give me this."

Plus side I dabble in f# which is so much more expressive.

Same for me in the Scala vs. Java world, it's hard once you get used to how awesome expressions over statements and algebraic data types/case enums/"discriminated unions" are. But I haven't done much C# (yet) myself, could you clarify for me: does C# have discriminated unions? I didn't think the language supported that (only F# has them)?

The c# team is working on a version of them they are calling Typed Unions, not guaranteed yet but there is an official proposal that I believe is 2 weeks old.

https://github.com/dotnet/csharplang/blob/main/proposals/Typ...

Cool, thanks for answering

Depends on the language. if you have destructuring you can do it all at once.

So like I believe you can do this in Rust (haven't written it in a while, I know it has destructuring of tuples)

let (a, b) = if (condition) { (1, "hello") } else { (3,"goodbye") }

.. save yourself an else :

int value1 = 128;

int value2 = 256;

if (condition) {

    value1 = 8;

    value2 = 16;

  }

It’s only an acceptable workaround in the case of two conditions, but you’re still out of luck if you have >2 branches and no match expression.

You can technically do some craziness with nested ternary operators but they look awful and if you write them you will regret it later.

True, but I would have to categorize that as an unacceptable workaround haha

Reply on news.ycombinator.com