I like Rust, and I'm probably missing something, but do I feel that some things should be easier. At times the language (or standard library, I suppose) feels a bit unwieldy. For example, trying to coerce a string from certain types:
let path = Path::new(&app_path)
println!("file name: {}", path.file_name().unwrap().to_str().unwrap());
Hopefully this is just a case of unfamiliarity, but surely something like should be easier?
If you were willing to allow for potential escape characters and acknowledge (to the user) the fact that the path might not have a file name, you could write:
println!("file name: {:?}", path.file_name());
or just for escape characters, but only if the file name existed:
if let Some(name) = path.file_name() {
println!("file name: {:?}", name);
}
Note that the unwrap() isn't boilerplate, in either case: if you are using `unwrap()` you are implicitly saying that you know for a fact that the file name is present (the first time) and a valid UTF-8 string (the second time), which isn't guaranteed in the general case on all platforms. If you wanted to write this more robustly, and these weren't guaranteed, you would need to explicitly take care of those cases.
I/O has lots of tricky error cases, and Rust usually requires you to acknowledge that. You can avoid dealing with those cases with unwrap(), or you can explicitly handle them. Personally, I much prefer this to being surprised only when the weird error case unexpectedly turns up because I never considered the situation in question, and that's generally how Rust handles things, but it depends on the task. It may make Rust less appropriate for quick scripting tasks, for example, where the domain is well-defined and the script is not likely to be reused (but I find that those scripts have an annoying way of getting reused anyway).
However, rust would be relatively well-suited for a "dirty quick scripting task". You could make a more traditional wrapper for the operations you like to use that assumes these rare edge cases don't happen, and panic otherwise.
This is sort of rust's philosophy; being explicit. Rust has no problem with failing, it just has a problem with failing without you telling it to. If you write a wrapper that implies you are willing to fail on these cases, then you're being explicit by choosing to use these functions instead :)
Yes, it's true. Code like this is going to be more verbose. Often, it's due to Rust being a systems language and exposing low-level details to you, combined with the type system ensuring safety. In this instance, `Path` is actually fairly complex. From the RFC: https://github.com/rust-lang/rfcs/blob/master/text/0474-path...
> The design of a path abstraction is surprisingly hard. Paths work
> radically differently on different platforms, so providing a
> cross-platform abstraction is challenging. On some platforms, paths
> are not required to be in Unicode, posing ergonomic and semantic
> difficulties for a Rust API. These difficulties are compounded if one
> also tries to provide efficient path manipulation that does not, for
> example, require extraneous copying. And, of course, the API should
> be easy and pleasant to use.
So, in this case, you have to call `file_name` to get the filename, but that returns an `Option`, since it might not be a file, it could be a directory. The `unwrap` says "crash if it's not a filename." You then have an `OsStr`, which is a string type that handles the kinds of cross-platform issues alluded to in the above paragraph. `to_str` will then attempt to turn it into a `&str`, but because `&str` must be unicode, if the conversion fails, it _also_ returns an Option, which is the last unwrap.
In systems programming, details matter. As such, our stdlib APIs try to expose those details. I expect some people will write higher-level abstractions that hide all this if you don't care as much.
"Often, it's due to Rust being a systems language and exposing low-level details to you, combined with the type system ensuring safety."
I'm not convinced it's being a "systems language" (in the sense I think you mean). The last three languages I've learned to fluency have all, in various ways, been very concerned about errors: Erlang, Haskell, and Go. Yes, they have widely varying opinions about what to do with them, but they all agree that you have to be fairly constantly worried about them. You can't sweep them under the rug; you need a strategy, and you need to deal with the resulting issues head on.
Despite their differences, what I feel like I've learned from them is that historically speaking, the vast majority of popular languages and their communities have been downright cavalier about errors. It's often in all the little details rather than a consistent, stated design goal, but the presence of various nils and nulls, APIs that will happily return empty strings for paths instead of errors, and all kinds of APIs and libraries that seem to be subconsciously written with the belief that returning an error is a failure on the part of the library and will go to what now seem to me to be absurd lengths to somehow keep klunking along in the presence of already-manifested failure. Even for languages that think they're being really good with exceptions, I find that when I go back to them, they end up using the exception support to "permit" themselves to be sloppy and hope the exceptions will pick up the pieces... and they often don't. Not because of some theoretical weakness, but because allowing developers to think they don't have to think about the error cases means precisely that they don't!
People are used to errors not poking them in the face until deploy time. It seems to me there's a strong, broad motion towards developing languages that will in one way or another force you to deal with them at compile time. It's a culture shock for people, but, I'll tell you this, get really good at Rust or any of these other languages and go back to any of those other languages, and you will find your code changes in those other languages to suddenly look a lot more like your Rust does anyhow, which means this putative disadvantage of Rust evaporates anyhow. Once you see how sloppy you were being, it's hard to go back in good conscience.
Great comment. I have run into this problem exactly in inherited codebases at my last couple of jobs:
> libraries that seem to be subconsciously written with the belief that returning an error is a failure on the part of the library and will go to what now seem to me to be absurd lengths to somehow keep klunking along in the presence of already-manifested failure.
It's a big problem with hairy repercussions if this idea is allowed to take root.
> The last three languages I've learned to fluency have all, in various ways, been very concerned about errors
Yeah, maybe I should revise my statement a bit: systems languages, overall, tend to expose more details. I meant this in a broader context than errors. As a simple example, manual memory management exposes more details than GC. There are many languages that care dearly about errors, as you've rightfully pointed out.
I broadly agree with the rest of your post. Error handling is hard and tedious, and programmers don't like doing it. I myself had an embarrassing bug in `rustbook` where I did `let _ =`. I only intended to start off that way! Programming is hard. But using Haskell, Rust, and other languages like this have certainly changed my code in other languages.
That would be nice, but as others hinted that wouldn't actually work:
* there are paths without a file_name (`/`) so it returns an Option to make that evident
* to_str attempts to convert the OS-dependent thing to a Rust string. Rust strings are valid unicode, but many filesystems don't have such strict requirements[0]. Again Rust returns an Option to makes that evident although there's a "to_string_lossy" method which will simply replace invalid sequences with U+FFFD if you don't really care
The Rust philosophy is generally to expose these issues upfront and force the developer to consider them (and either handle or explicitly ignore them). It is indubitably less convenient than e.g. Python 3's `PurePath(app_path).name` returning an str, but you'll have had to decide what happens in case of failure.
Paths are really a good example of something which looks simple, should be simple, and is actually anything but simple for historical and technical reasons, especially in a cross-platform context.
[0]
* Unix paths are the most troublesome: they're arbitrary bags of (non-NUL) bytes, they don't have to be in a known encoding, they don't have to be in any encoding.
* Windows paths are not guaranteed to be Unicode either: they're UTF-16 code units aka UCS2 + surrogates, and the surrogates may be unpaired, leading to invalid Unicode.
Also, OSX applies unicode normalization to the filenames, which can cause some interoperability problems with unix, e.g. you try to copy files forth and back between the systems and end up with two copies of a file, with identical-looking filenames that differ in their unicode normal form.
To add to the other comments, Rust prefers to make error cases explicit. We have memory safety. You can opt out of it, but you have to opt out explicitly. We have exhaustive match. You can use a wildcard, but you need to explicitly do so. We have nullables and Results. You need to explicitly acknowledge the error/null case, or use `unwrap()` to say that you don't mind a panic at this point.
This leads to verbosity at times, but usually its a good verbosity.
I'm sure I'm not the first (or the hundredth) to say this, but `unwrap` has always struck me as a horribly innocuous spelling of "yes, feel free to crash here".
I presume there is (or could be) a standard lint to prevent this getting into production code, but it still feels kind of icky.
Dammit, I kept wondering why it wasn't named unwrap_or_panic/unwrap_or_assert but it could be worse at least unwrap is a less friendly name then scala's get.
Just my 2cs, but the complexity of this code is here to remind you there are a lot of cases you have to take into account :
let path = Path::new(&app_path);
if let Some(ostr) = path.file_name() {
if let Some(str) = ostr.to_str() {
println!("file name : {}", str);
} else {
println!("WARNING : file name is not a valid unicode sequence ! (file name : {:?}", ostr);
}
} else {
println!("Path is either a root directory or a dot entry, it has no filename");
}
Where familiarity comes in I believe is in what that line communicates to me: There might not be a file name (like having '/' as path), and that getting a string slice out of it might fail (the kind of string the platform uses for paths might not be UTF-8 compatible).
Plus, the unwrap()s tell me that whoever wrote the code considered it an assertion failure if one of those is happening.
I read a lot more Rust than I write, and it really helps that the code communicates a lot. And with knowing about OsString/OsStr beforehand, I only had to lookup when file_name() returns None, the rest is rather implicit by convention, or familiarity.
Presumably you mean String/&str? (~str hasn't existed for a long time.)
On the contrary, the lack of the string/string-view distinction is widely considered a flaw in the C++ standard libraries. C++14 introduces std::string_view to correct it. Rust's String/str distinction is just the same as C++14's std::string/std::string_view.
Apart from the Rust's usual rule to invent some abbreviations, but only apply them half the time.
Then "types start with an uppercase letter" except when the language creators break their own rule.
Then the fun "sometimes we use () and sometimes we use [] to do practically the same thing".
Then the various insanities with ::.
Then Generics. How many examples of languages which tried to use <> for Generics do we actually need before people learn the lesson?
I really wished some people took Rust, and wrote a new frontend to get rid of all the pointless inconsistencies and other "C did, so it has to be good"-isms (like_all_this_underscore_stuff or the ridiculous abbreviations), because many ideas of Rust are not only good but brilliant and deserve to be put into languages which don't belong to the purely-academic category.
I really wish Rust to succeed, but can we stop this approach of "3 steps forward and 2 steps backward" to language design?
>
Apart from the Rust's usual rule to invent some abbreviations, but only apply them half the time.
Do you have an example?
> Then "types start with an uppercase letter" except when the language creators break their own rule.
They always start with a capital letter, except for built-in types or FFI bindings to libraries such as libc where the original types used a lowercase letter. This convention is exactly the same as Java.
> Then the fun "sometimes we use () and sometimes we use [] to do practically the same thing".
I've never heard this before. Do you have an example? () is used for function calls, grouping, and tuples, while [] is used for array literals and array indexing.
> Then the various insanities with ::.
The double-colon is very useful so that you can tell the difference between module lookup and field projection/method calling. Early Rust used . for module lookup, and it was confusing to tell at a glance whether a function was being called or a method was being invoked.
> Then Generics. How many examples of languages which tried to use <> for Generics do we actually need before people learn the lesson?
Using square brackets like Scala wouldn't actually help with the ambiguity, because it would be ambiguous with array indexing. The only syntax I've seen that actually solves the ambiguity is D's `!()`, which was deemed too unfamiliar. Angle brackets were chosen because they are familiar and aren't really any worse than the other mainstream options.
> I really wished some people took Rust, and wrote a new frontend to get rid of all the pointless inconsistencies and other "C did, so it has to be good"-isms (like_all_this_underscore_stuff or the ridiculous abbreviations)
The underscore naming convention was actually taken from Python's PEP 8. Rust doesn't really have any more abbreviations than most other languages at this point.
> > Then the fun "sometimes we use () and sometimes we use [] to do practically the same thing".
> I've never heard this before. Do you have an example? () is used for function calls, grouping, and tuples, while [] is used for array literals and array indexing.
Maybe referring to the ability to use either type of brace with macros?
Yeah, you can use any type of delimiter with macros, but I think that's an important feature, especially since macros can expand to declarations. Early versions of Rust required parentheses for all macro invocations, and that looked really ugly for anything that looked like a block. Delimiter interchangeability is a feature from Racket that works really well when it comes to macros and I'd hate to give it up.
Agreed. They allow you to naturally create vectors with the bracket delimiter `vec![1, 2, 3]`, create spawn-like macros with the brace delimiter `spawn { code }`, and in the normal case just use parentheses `println!("testing")`
> () is used for function calls, grouping, and tuples, while [] is used for array literals and array indexing.
Array indexing is a function call, because an array is a function from its index set to the set of the values the array stores, or -- equivalent -- a partial function from integers to the value set.
I don't know, I never liked how all FunctionNs are sort of "unofficial" partial functions (because they may throw), and PartialFunctions are then made a subtype of FunctionN, because they have an extra method where you can ask whether they are defined at given points. Especially since throwing seems to be falling out of favor in Scala, being replaced by Try[] return types.
This is an orthogonal issue. Arrays are clearly partial functions. The Try[.]-vs-exceptions issue is to do with the question whether failures should be reflected in types (the Try[.]-option) or not (exceptions). There are good arguments for and against both options, but both options go well with the understanding that arrays are functions and indexing is function application.
I don't think anything's much orthogonal to partiality of functions in languages with strong type systems, unfortunately :)
You wrote that array indexing is "a partial function from integers to the value set". If we're to take the suggestion seriously, then the practicality of it depends on how partial functions are represented in the language. Which itself is certainly not orthogonal to the Try-vs-exceptions issue.
I'm not sure I can agree. I didn't say that the type of the array function is independent of the choice of error propagation mechanism. If you think an array is a partial function from integers to some value domain, say A, then in the exceptional POV the array type is int -> A, and in the Try[.] POV the array type is int -> Try [ A ].
I was talking about the mechanism for array indexing.
In both cases, indexing is function application. So the choice of error representation is orthogonal. This is even more evidence that we should not use a different operator for array indexing as Rust does alas.
It says a lot about Rust's culture. If they are not only _not_ interested, but actively hostile towards input, why should I bother?
Just look at the replies. Sure, it's possible to hand-wave issues away by setting the standards low enough with "Java did that mistake, too", "we just copied that from Python", "this looked more familiar" ... I think no one disagreed with that.
It's 2015, and having marketing along the lines of "we only made half of C++' mistakes" just doesn't cut it for me anymore.
For other people it might be good enough, but I'm worried that Rust won't get enough traction if the language is not drastically better on average than its incumbents, but just messy in different ways.
First off, Rust != Hacker News. You might have been downvoted by someone unaffiliated by Rust on HN. For example I'm affiliated with Rust community but didn't down-vote you.
Second, let's review your post:
You never supplied examples to your comment of using some abbreviation only half of the time.
Your point about Rust using [], () and {} for functions is wrong, because it only ever uses () for function calls, others can appear in macro.
Your example of using <> vs [] is a subjective choice, that doesn't have any scientific or even majority consensus. To make matters worse, one of Rust's side goal is to somewhat ease migration of C++ programmers to Rust. I actually agree with you on this point, but I realize most people would find this syntax confusing due to habit of writing array literals using brackets.
On the other hand underscore python style that is proven by a study[1] to be a better choice for readability you consider the less usable one.
It is perfectly fine that many design choices in Rust evolved from "let's copy what $random_language did", but mentioning the drawbacks of that kind of approach to language design suddenly requires "scientific studies demonstrating your points"?
Are you kidding me? That's exactly what I meant with "Rust people are actively hostile toward input".
It is even more "I don't want to hear what you say" than it appears on the first look, because we both know that counting all "scientific studies" about language design probably wouldn't require more fingers than a human usually has.
So all we have is some empirical knowledge. You even got some findings for free! Things no one ever said:
- "Having two different ways to call/invoke/execute stuff
made it much simpler to learn the language."
- "Making the casing of types inconsistent really helps
when reading code."
- "Dropping random characters in functions and types made
me feel at home coming from C! I would be terribly
confused if ptr was called pointer, vec vector, fmt
format, iter iterator or rt runtime. The only thing I
don't like is FromStr, it should really by FrmStr
instead! .. I love str's rsplitn btw!"
- "Calling Strings Strings and String views str ... that
makes a lot of sense!"
- "Having used both <> and [] extensively, <> is much
more readable."
- "It was a really great idea to have special syntax for
arrays, so the language designers could overload []
with two completely different meanings."
- "Having both () and [] available is great because you
can write code where foo(x) and foo[x] do different
things!"¹
- "Not having varargs really worked out! Nevermind that
most popular macros exist solely to emulate varargs!"
- "Despite most macros not needing the do-whatever-
you-want syntax, let's require ! for all of them. This
way, macro writers don't have any reason left to try
making their macros behave predictably! Isn't it great
that they can just claim 'you knew that all bets where
off when you wrote that !, so stop complaining!'
instead of fixing their macro?"
- "Fucking up Generics so badly that it requires
different ways of writing them depending on the
context really paid off. It's certainly not an issue
which is hit by every person writing something Generic
for the first time."
- "Inventing unnecessary differences between modules and
objects is great, because it forces you to think
whether you need to use . or :: and breaks use-sites
of that code when migrating from one to the other."
- "Given all the lessons of terribly broken dependency
management systems out there – let's just ignore them
all and put every package in a global namespace ...
what could ever go wrong?"
The language could have been much better if Rust devs wouldn't have been so insecure and defensive, but now it's too late anyway.
So why bother evoking any more excuses in different places? Rust-the-bad-parts is basically unchangeable now.
So what's left? I think it's only honest if Rust devs would be more open about the mistakes they made, and wouldn't require outside expertise to point out the issues.
¹ WAIT ... that's actually what Rust devs said when they defended having both () and [].
but mentioning the drawbacks of that kind of approach
to language design suddenly requires "scientific
studies demonstrating your points"?
Are you kidding me? That's exactly what I meant with
"Rust people are actively hostile toward input".
For what is worth, I only meant it in case of underscore, since underscore syntax has scientific proof it's more readable, if you are aware of a better or another study, please list them. Also I asked for examples.
But here let me look at your complaints:
1) Not sure what you mean in this case, could you elaborate
2) Type casing is inconsitent. All types are CapitalCamelCase. Only special built-in literals are lower case.
3) Fair point, a bit subjective, but fair. I like the terse syntax tbh.
4) Well, String represents mutable and str represents immutable strings, which also double as string views.
5) Fair point, I prefer [] for generics, but again it still falls under subjective.
6/7) I'm unsure what you mean. [] is used for indexing arrays or slicing a piece of it. I think Python had something similar.
If you have foo(x) that's always AFAIK calling function. foo[x] means it's calling index or slice operator on a foo. In either case it's taking a portion of foo.
7) see 6
8) That's actually a fairly good point. I think some kind of optional parameters or varargs were planned, but unsure of current situation
9) Not getting what you mean here? Whenever you add extensibility to language via macros or custom operators, you get weird language DSLs that are incomprehensible. At least putting macro_name! tells you next part is DSL and what's its name is, so you can look it up.
10) Fucking up generics? What?
11) Not sure what your point is? Rust doesn't have objects. It has structs and it has traits. Modules are merely way to organize code. I think you are probably referring to OCaml like modules/objects, but unsure what.
12) Fair point. I'm unsure what alternatives you have in mind? Using URLs?
1) You basically have both () and [], wasting one of the scarcest
resources in syntax (brackets).
Some people might argue that getting a value from an array is totally
different from getting the same value from a function or a map, and
deserves special syntax. If we look at languages which did away with
this made-up difference we see that pretty much no person is missing
it.
Even if you disagree with this reasoning and consider arrays to be
something very special, deserving its own syntax – guess what? Rust
developers introduced the traits Index and IndexMut, so all the great
ideas about some type being special and knowing what happens when you
read [] went straight out of the window.
If we dig deeper and try to understand why they did something so
astoundingly mis-designed, we basically hit an interesting issue:
They overloaded their [] operator to do two completely different
things, depending on whether there is an & in front.
Thing A: return the value at the given index
Thing B: return an address pointing into the indexed data
This of course doesn't translate well into the () syntax, given that
Rust devs are proud that they don't support overloading.
(I guess []'s overloading doesn't count for some reason ... and doing
the little dance with traits doesn't count either.)
Taking a step back, if it would have been considered acceptable to
pick two different names for doing two different things, the whole
issue wouldn't exist, e. g.:
Thing A: values(1)
Thing B: values.at(1)
2) Yes, we agree. Having different sets of rules for a) language
designers and b) language users has shown consistent results:
It never worked out.
3) Yes. I have nothing against terse syntax, it should just be
consistent. (I favor not abbreviating things though, because it's
difficult to be both terse and consistent, considering that things
can be abbreviated in more than one way.)
4) Yes, I know what they do. I just thought it was a nice example of two
related constructs having different casing style and abbreviation
style.
6/7) See 1). The sad thing is that [] can do whatever the developer
wants. All guarantees went out of the window with Index/IndexMut.
9) What I meant was that not every macro wants to define some weird
language DSL. There are plenty of things which only exist as macros
because the language lacks varargs. (vec! for instance.)
If the language ever adds varargs, vec! can't just stop being a macro,
because that would break source compatibility: They would need to keep
the macro version of vec and introduce a new non-macro version of vec,
and hope people migrate from vec! to the "new" vec.
It's a design which makes the common 90% suffer for the benefit of the
most complex 10%. Sometimes it is worth it, but in this case I think it is
not.
10) I had the combination of picking a symbol which is both hard to read and
hard to parse in mind.
Every language that chose <> has weird cruft and therefore it shouldn't
haven been too surprising that Rust is also suffering issues, but in
Rust's case the problems have been shokingly severe. There are loooong
discussions about it if you want to read them. (So it's not just me.)
11) Sorry, I meant structs.
12) URLs are an option. There are also alternatives. I think the essence is
that it's possible to deal with these issues without entering Java's
tld.mycompany.mycontinent.mygroup.myproject.mydogsmiddlename madness.
Re 1, 6 & 7, as we've discussed before: languages that do away with the () vs. [] distinction don't have the same restrictions as Rust, e.g. Scala doesn't have explicit addresses for objects, meaning `&x[i]` in Rust (get the address of the `i`th element) has no first-class equivalent in it. It isn't possible to implement this by just overloading `()` without introducing dramatic new language features.
On this note,
They overloaded their [] operator to do two completely different things,
depending on whether there is an & in front.
is entirely wrong: `x[i]` is literally equivalent to `x.index(i)` or `x.index_mut(i)` depending on mutability, so the `&x[i]` form is the same as `&x.index(i)`, and `&` is a no-op. There's no special magic other than a slightly subtle desugaring.
No Rust dev is proud that there's no overloading... that sentence doesn't even make sense, as every operator can be overloaded, including the () call syntax.
Now I agree that there's often room for improvement in designs, but hammering on a relatively minor syntactic point (especially one that follows many, many other languages) for months seemingly without understanding the current design and the reasons for it is quite tiresome.
1) Sure, pair symbols are a bit rare. But they aren't as rare as you set them to be. Symbols like / | or \ can act as substitute for bracket like syntax.
> If we look at languages which did away with
this made-up difference we see that pretty much no
person is missing it.
Eh, not sure what languages are these and how you think they relate to Rust. Keep in mind Rust goal almost from the start was something that is familiar to a people that worked with Gecko engine. With that in mind, I can't think of a similar family language that did this.
You know what happens when you call Index/IndexMut. To say it isn't so, is outright fallacious.
Also Rust takes the probably best road of allowing limited operator overload, which IMO so far proved better than allowing no operator overload or allowing custom operator overload - which is subject to weird rules and/or leads to heavily overloaded code.
Also [] always does same thing. For given Index value it returns value found at that index. & is not an address. AFAIK address are never allowed unless you drop into unsafe. It's a borrow reference to Output value. Index returns immutable version, while IndexMut takes mutable version and returns mutable output value.
2) No we don't. I think having user and built-in defined types is perfectly ok. In any non-Lispy langugage there are special literals, which can't be handled by user defined ways, unless you allow for some funky grammar.
4) Related yes, same no. In same way i32 and u32 are related but not the same. As I said in previous question having some subset of language be unable to modify is IMHO a good thing.
6/7) They can't. You can tell by mutability of array which one will be called and which one will be returned. You CAN'T EVER change type of mutability of result.
9) Whenever I see macros/operator overload/syntax being given too much freedom, it always ends up with incomprehensible DSL-s that you can't disentangle from regular code.
10) Subjective opinion. And it could be trivially solved with better type aliases.
12) I don't think it's a big problem and a fix to Cargo that adds a special unique identifier should be trivial to implement, although not necessarily forward/backward compatible.
> Nobody claims that <> isn't "familiar". People are claiming
> that <> isn't very good, and they are correct with that.
> Those languages which made <> "familiar" picked <> because
> they added templates/generics/... after the fact and tried
> to bolt them onto an existing language without breaking all
> existing code.
What people are claiming this? Is there some argument
<Type, <Type<Type>>>
is much better than
[Type, [Type[Type]]]
in monospaced fonts? I agree I prefer it, but I know it comes down to subjectivity and familiarity. Not the most compelling reasons.
> As you might see, they are called i32 and u32, not i32 and UnsignedInt4Bytes.
Correct, because they are both built in literals. String isn't a built in literal. You can't have:
u32::new()
>Not sure what you suddenly try so say with "you can't
>modify this", "you can't mutate that".
>As shown in 1) [] can do whatever the developer implements.
>Sure, the usual language rules apply, I think nobody
>disagreed on that.
No matter how many time you call Index on your array it stays the same. What kind of trippy Index you want to implement is still there, only with uglier syntax.
> Yes, that's exactly the concern I'm raising here, because that's what Rust is encouraging.
It's not. All macro invocations are fenced in by macro calls. All syntax extensions are followed by extension calls. Could macros/syntax extensions do horrible things? Sure. So can regular code.
Not only are all your points about Rust incorrect, but numerous people in both this thread and past threads have repeatedly told you why they your points are incorrect and yet you persist in believing that they have been unaddressed. At this point it's safe to say that observers have caught on to your campaign of indefatigable misinformation and find it easier to downvote your comments than to waste any more of their time making arguments that you will proceed to blithely ignore.
In fact, it says a lot about Rust's culture that people were willing to engage you constructively in the first place despite your acerbic and technically-naive ramblings.
In this example the dichotomy is between String (which is guaranteed by the type system to be valid UTF-8) and OsStr (which might be in an unknown encoding or otherwise not decodable to valid Unicode).
This is exactly when you want a systems language to require explicit conversions, rather than converting things silently and possibly losing or corrupting data.
I understand the difficulty in this space; much of it is caused by forcing the Windows unicode filesystem API onto python as its world-view, rather than sticking to the traditional Unix bytes world-view. I'm unixy, so I'm completely biased, but I think adopting the Windows approach is fundamentally broken.
The problem there is overblown - it's basically all due to the idea that sys.stdin or sys.stdout might get replaced with streams that don't have a binary buffer. The simple solution is just not to do that (and it's pretty easy; instead of replacing with a StringIO, replace it with a wrapped binary buffer). Then the code is quite simple
import sys
import shutil
for filename in sys.argv[1:]:
if filename != '-':
try:
f = open(filename, 'rb')
except IOError as err:
msg = 'cat.py: {}: {}\n'.format(filename, err)
sys.stderr.buffer.write(msg.encode('utf8', 'surrogateescape'))
continue
else:
f = sys.stdin.buffer
with f:
shutil.copyfileobj(f, sys.stdout.buffer)
Python's surrogateescape'd strings aren't the best solution, but I personally believe that treating unicode output streams as binary ones is even worse.
