This is why I never write shell scripts more than about 4 lines long or with any control flow statements in it -- I use Python for that. The Python might be a bit longer, but at least I'll understand it when I come back to it 6 months later.
Source code is Unicode? Great.
Forcing _everything_ to have an Encoding when the surrounding world isn't an academically clean environment? Nope, this means Unicode Enforcement and Error Handling in what should be simple programs.
I don't mind have __optional__ libraries for handling Encoding conversions, corrections, and errors... but if I'm working with a legacy filesystem, human input, or anything else, the only basic language support I want or need is transparency of bits/bytes. Let a programmer decide if or where things are validated and what to do about handling invalid input at that moment; do not force the issue upon them.
Python did eventually acquire a sensible (lossless, errorless) way to convert back and forth between binary and Unicode — UTF-8B, known as surrogateescape, described in PEP 383. Unfortunately, it isn't the default everywhere. PEP 540 makes it default in some cases.
This is the reason Oil is written in its own private fork of Python 2 instead of in Python 3.
To me this is the same problem I had with HTML and DOM mentioned on the other thread (which I will reply to!).
The analogy is
HTML files : DOM :: string data :: Python strings.
A lot of software is basically "undoing" problems caused by other software, not addressing something in the application domain. PEP 383 and 540 seem to be clear instances of that. (And note that I said Python is an amazing achievement in the appendix of this post, which is simultaneously true :) )
Woah. If you're using a dynamic programming language for mission-critical software and your tests don't properly cover "coercing binary data into a Unicode string", then your problems run way deeper than Python 2 vs 3.
This isn't restricted to on-orbit software. Your GSE ("ground support equipment", for those not in the industry) also shouldn't have that kind of quality problems.
In defense of Satellogic, it never would have gotten off the ground using traditional risk-minimizing aerospace engineering practices. And it's arguable whether the software in question was "mission-critical" — the mission did continue, after all. My efforts to raise the bar on software, process, and documentation quality were not appreciated.
Ah, I missed that bit. Still, that sounds to me like a problem with Python's attitude in particular, and with the attitude of many (not all) dynamic programming languages in general, and not so much with a problem of Python 2 vs 3.
> In defense of Satellogic, it never would have gotten off the ground using traditional risk-minimizing aerospace engineering practices.
Having worked for several years in the traditional space industry: Yes, I totally get what you're saying. In fact, the paperwork-heavy quality assurance we have to satisfy, which is more concerned with formalities than with actual hardware/software quality, probably would have missed that case as well.
Do you have testing coverage metrics for exception handling? In my experience outside Satellogic, that's one of the places testing usually misses, especially in languages with Python's attitude, which I agree is not well suited to on-orbit code.
I have not personally come into contact with software PA/QA requirements, only with those for FPGA designs (VHDL in particular). In my largest project, I had to meet 100% statement coverage, with documented justifications for any uncovered lines. Typically, in such an environment, exceptions are a no-go for flight software.
There are several notes on "failure-free programming" in Dercuano; maybe you'd be interested. Essentially I came to the conclusion that although purely local restrictions (like not allocating memory or raising exceptions) can be helpful, I don't know how to structure a program so that all of the desired safety properties can be checked locally, except for very simple programs. Let me know what you think if you do check it out; I'd be interested in your opinion.
But yeah I still think that idea has merit... Somewhere on my blog I made the observation that Python 3 and Perl 6 are both worse than their predecessors for the shell scripting domain. They're better languages in general, but worse for that domain -- which is still important and getting bigger along with the rest of computing, IMO.
I think Oil would be useful in any case, but both Python 3 and Perl 6 opened up that gap in the design space even wider. I mean the string is the CORE TYPE of such programs, so it's important that it be logically applicable to the problem.
I'm sure many people saw the Mercurial / Python 3 thread on HN last week: https://lobste.rs/s/pnuak4/mercurial_s_journey_reflections_o...
Basically the same story, although I questioned their decision of not embedding the Python 2 interpreter instead. I think the only reason not to do that is "memes".
With regards to being better / worse in the shell scripting domain, I would say that currently performance wise, Perl is better for shell scripting. But development of shell script-wise, I think Raku has superior handling of command line parameters built in: https://docs.raku.org/language/create-cli
In golang strings are immutable sequences of bytes (which can be concatenated) or have 'slices' taken from within them (I believe addressed to a rune; which IIRC is a complete UTF-8 sequence). Standard libraries typically operate with bytes[] for low level operations (file I/O) but strings and bytes can be coerced between each other with ease, and notably many objects (such as a File https://golang.org/pkg/os/#File.Write ) have methods for interacting with bytes[] and strings.
There's a core library specifically for low level Unicode operations and external libraries for more complex tasks.
(This, coincidentally, was also the problem in Python 2, and why Python 3 breaking the world was necessary, if inconvenient for some.)
At this point, the only sensible design for strings is as fully encapsulated, opaque values that are emphatically not arrays of anything. If you want to index them, you should be specifically saying what you want - nth byte, nth codepoint, nth grapheme etc. If you want content as an array of bytes in a particular encoding, then you should ask for that specifically. Internally, yeah, it should use UTF-8, because it makes the most sense - but that's just an implementation detail.
So far, the only language I know that got this right is Swift.
So, while there's a tradeoff in elegance I do think it's logically very simple. I do think the Rust approach for example is more "correct", but it's also tedious to work with and I think the ergonomics matter (can't speak for swift).
Example: https://play.golang.org/p/7XWC9Irui3N
x = abc
3 vs 3
y = é
3 vs 2
z = 世界
6 vs 2
s>>r 0 1 true e
s>>r 1 2 true ́
[]b>>b 0 true true 00000065
[]b>>b 1 false true 000000CC
[]b>>b 2 true false 00000081
(not putting in a code block given the above and mobile...)
package main
import ( "fmt" "unicode/utf8" )
func main() { var x, y, z string; x = "abc"; y = string([]byte{0x65, 0xCC, 0x81}) // 'e' + 0x0301 ( 0(011 00)(00 0001)) = "é"; z = "世界"; fmt.Printf("x = %s\n%d vs %d\n\ny = %s\n%d vs %d\n\nz = %s\n%d vs %d\n\n", x, len(x), utf8.RuneCountInString(x), y, len(y), utf8.RuneCountInString(y), z, len(z), utf8.RuneCountInString(y)); for k, v := range y { // iterates as runes, not string slices //fmt.Printf("s %d\t%s\t%v\t%s\n", k, utf8.RuneCountInString(v), utf8.ValidString(v), v); fmt.Printf("s>>r %d\t%d\t%v\t%c\n", k, utf8.RuneLen(v), utf8.ValidRune(v), v); } for k, v := range []byte(y) { // iterates as byte units, not runes fmt.Printf("[]b>>b %d\t%v\t%v\t%08X\n", k, utf8.FullRune([]byte{v}), utf8.RuneStart(v), v); } }
The world is not only about English and ASCII.
People who want these shortcuts usually don't understand what problems Unicode and character encodings solve in general. And that's exactly what produces software that won't allow me to properly enter my Hungarian name as it is, with diacritics.
It's utterly inexcusable and lazy and stems from an annoying sense of Anglo superiority.