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> Hoogle doesn't seem to find me a function like Rust's .get() in the standard library In practice, you don't really need one - the safe alternative to "xs !!

> Hoogle doesn't seem to find me a function like Rust's .get() in the standard library In practice, you don't really need one - the safe alternative to "xs !! n" is pattern-matching on the result of "drop n xs", as that's [] if xs has ≤n elements: https://www.haskell.org/onlinereport/standard-prelude.html#$vdrop https://www.haskell.org/onlinereport/standard-prelude.html#$...

masklinn 6y ago
> In practice, you don't really need one - the safe alternative to "xs !! n" is pattern-matching on the result of "drop n xs", as that's [] if xs has ≤n elements: Great so instead of `xs !! n` you're supposed to write case drop n xs of [] -> … x :: _ -> … that seems… less than likely?
geofft 6y ago
Sure, that seems syntactically more cumbersome than 'if let Some(foo) = xs.get(n)' or 'xs.get(n).map(|foo| ...)' in Rust, but yes, you can do it. As I said, because both the Rust and Haskell versions are more cumbersome than using the version that raises an exception/panics, both Rust and Haskell's standard libraries choose to give you a syntactically-easier alternative that isn't a total function. All I'm saying is that Haskell doesn't seem to do anything different here - Rust has incorporated the lessons from Haskell's type system. (As someone who fell in love with Haskell a long time ago but never got to use it professionally, this is basically why I like Rust.) Is there something Haskell does that Rust does not do? I'm not trying to say Haskell is insufficient - I'm just refuting the claim that Rust is insufficient and should act more like Haskell.
- EvilTerran 6y ago
  Sure, I don't disagree - I meant only to add context for anyone reading who was unfamiliar with Haskell, lest they come away with the impression that the lack of a .get()-equivalent was some kind of egregious oversight.

masklinn 6y ago

> In practice, you don't really need one - the safe alternative to "xs !! n" is pattern-matching on the result of "drop n xs", as that's [] if xs has ≤n elements: Great so instead of `xs !! n` you're supposed to write case drop n xs of [] -> … x :: _ -> … that seems… less than likely?

geofft 6y ago

Sure, that seems syntactically more cumbersome than 'if let Some(foo) = xs.get(n)' or 'xs.get(n).map(|foo| ...)' in Rust, but yes, you can do it. As I said, because both the Rust and Haskell versions are more cumbersome than using the version that raises an exception/panics, both Rust and Haskell's standard libraries choose to give you a syntactically-easier alternative that isn't a total function. All I'm saying is that Haskell doesn't seem to do anything different here - Rust has incorporated the lessons from Haskell's type system. (As someone who fell in love with Haskell a long time ago but never got to use it professionally, this is basically why I like Rust.) Is there something Haskell does that Rust does not do? I'm not trying to say Haskell is insufficient - I'm just refuting the claim that Rust is insufficient and should act more like Haskell.

EvilTerran 6y ago
Sure, I don't disagree - I meant only to add context for anyone reading who was unfamiliar with Haskell, lest they come away with the impression that the lack of a .get()-equivalent was some kind of egregious oversight.