What are some mind blowing Rust tricks? (programming.dev)

submitted 1 month ago* (last edited 1 month ago) by little_ferris@programming.dev to c/rust@programming.dev

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If we were to create a Rust version of this page for Haskell, what cool programming techniques would you add to it?

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[-] barsoap@lemm.ee 1 points 1 month ago* (last edited 1 month ago)

Rust has impl Add<&str> for String and impl AddAssign<&str> for String. Both append as expected.

I wouldn't go so far and say "as expected": "Addition" implies that we're dealing with a ring, that there's also multiplication, and that really doesn't make sense for strings (unless you indeed consider them numbers). It's why Haskell's Monoid typeclass comes with the function mappend, not madd.

In Rust's defence though std::ops traits aren't meant to carry any semantics they're about syntax: It's called Add because it's +, not because it means something. I do think it would've been worth it to introduce ++ for general appending (also vectors, sets, maps, etc), though, to keep things clean. Also ++= for the mutating case.

[-] BB_C@programming.dev 1 points 1 month ago

I do think it would’ve been worth it to introduce ++ for general appending.

I already mentioned (val..).next() which is both safe* and explicit about it being a generic stepping operation instead of possibly being sugar for {x = x + 1; x}.

Also, calling it "appending" is weird for us folks coming from languages like C 😉

* you don't have to worry about what i32::MAX++ would/should return.

[-] barsoap@lemm.ee 1 points 1 month ago* (last edited 1 month ago)

Pre- and post-increment are only really useful when you're doing C-style looping and there's a good reason we don't do that in Rust.

I actually honestly can't recall ever making an off by one error in Rust, I'm sure when implementing specific data structures or when doing pointer manipulation it's still a possibility but you can write a gazillion lines of code without ever running risk of that particular annoyance. Also while C folks may have an argument regarding operator semantics, C++ folks don't they're doing unspeakable things to <<.

Also, FWIW Haskell uses ++ to append lists and therefore also strings. It's not like it's an odd-ball usage of the symbols, that'd be .. which I vaguely remember some language using. Would cause a whole new class of confusion regarding 'a'..'z' vs. "a".."z". Not to mention that "aa".."zz" actually makes sense as a range all that's missing is &str: Step. Probably not a good idea to have built-in because do we mean printable ASCII? Whole unicode range? Just the alphabet? Not an issue when you're doing it to single chars but strings get ambiguous fast. Does Rust even guarantee stuff about Char ordering C certainly doesn't really do that, short of I think 0..9 being contiguous.

[-] BB_C@programming.dev 1 points 4 weeks ago

It’s not like it’s an odd-ball usage of the symbols, that’d be .. which I vaguely remember some language using.

I take it, you don't bash/zsh/...?

[-] barsoap@lemm.ee 1 points 4 weeks ago

I try not to and if I have to I'd use string interpolation. I'm not even sure whether you're pulling my leg right know, I literally don't remember whether they have a string append operator.

Like 99.999% of the sh I ever wrote was in Makefiles and short wrapper scripts which could just as well be aliases. No argument handling past $@, no nothing the language is just too fickle for me to bother dealing with. The likes of zsh are make-up on a pig, I think I had a quick run-in with fish but never really got the hang. Nushell is different, it's actually bold enough in its changes to get rid of all the crufty nonsense.

[-] BB_C@programming.dev 1 points 4 weeks ago

Sorry, I thought you meant the use of .. in Rust is odd. So I pointed out that {0..9} and{a..z}is also used at least in bash and zsh. That's at least 10s of millions of users!

I know of .. being used for appending by lua at least. So still not odd-ball I would argue, since the people who interacted with lua code in their life probably outnumber those who interacted with all functional languages combined.

[-] barsoap@lemm.ee 1 points 4 weeks ago

Now that you mention it yes Lua is probably the one that I remember. It's an incredibly well-designed language from start to finish but also culturally an odd-ball. .. isn't even the biggest offender: Their indices start at 1. Haskell accosts you with zygohistomorphic prepromorphisms but at least [1,2,3] !! 1 is 2.