I’d argue back that this particular pattern, where you want a list of fixed length with the same value, is much better served by `List.duplicate/2`.
I think in general, higher order combinator functions like identity, const, flip, and friends are usually used to facilitate the point-free style of programming in languages like Haskell. And in general point-free style usually does not lead to the most readable code. Again, referring to the example provided, if I know anonymous functions, I know what’s going on. When using `Funcion.const`, I have to understand that concept as well. There’s one extra thing to learn. Michał. From: "elixir-lang-core@googlegroups.com" <elixir-lang-core@googlegroups.com> on behalf of Bruce Tate <br...@grox.io> Reply to: "elixir-lang-core@googlegroups.com" <elixir-lang-core@googlegroups.com> Date: Monday, 3 February 2020 at 11:47 To: "elixir-lang-core@googlegroups.com" <elixir-lang-core@googlegroups.com> Subject: Re: [elixir-core:9353] [Proposal] Add Function.const/2 My counterpoint is this. Any time you can name a concept that makes it easier to see what's going on, it's important. Examples: * Create back padding of four blank table cells * use with Stream.repeatedly and take, for example, to initialize a data structure for OTP. I do these two things with pretty good frequency because I build responsive layouts often needing tabular structure, but without HTML tables. Say you are laying out tables that are responsive but without HTML tables. You d want to add padding to the end of uneven rows. To create the padding you'd do Stream.repeatedly( fn -> :padding end) |> Enum.take(4) where :padding is the constant padding you want. This pattern comes up with some regularity in my user interfaces. It doesn't hurt anything, and it would be a great addition to the function module. I like this proposal. This is exactly the kind of function you'd expect to see in the module. +1 from me. -bt On Sun, Feb 2, 2020 at 2:42 PM Jesse Claven <jesse.cla...@gmail.com<mailto:jesse.cla...@gmail.com>> wrote: That all makes sense! I would say that in Elm it's used somewhat frequently. I don't have access to the previous code that I worked on (changed jobs), so unfortunately I'm unable to grep for `always` to find some good examples. In the codebase at my new job, there's a couple of places where `fn _ -> something` is (my original example in this thread). It's basically for anywhere you'd want to ignore some value, and always return something else. I tried searching through GitHub for that code sample but the search functionality was a little subpar. I understand about keeping the stdlib small, but for a relatively small function, and one that's considered "table stakes" in most FP languages, perhaps it would be a good fit? On Thursday, 30 January 2020 11:20:58 UTC, Wiebe-Marten Wijnja wrote: The reason `Function.identity/1` was added after it was requested many times previously, was that at some point everyone agreed that it would improve Elixir's documentation, because it is easier to search for than `&(&1)`. The `const` pattern is much less wide-spread. In e.g. Haskell it sees some use in places where it is the single (or at least by far the simplest) way to make things typecheck in a pure functional environment. In Elixir, I suspect that it would be used much less commonly. The fact that our functions contain statements that are executed from top to bottom and rebindable variable names means that we are even less likely to use it anywhere. As such, I don't think `const` is a function that is important enough to include in the standard library. Of course, I'm very much open to evidence of the contrary ^_^. Do you have any example code of where you'd see `const` being useful? ~Marten/Qqwy On 30-01-2020 10:24, Jesse Claven wrote: Hey Amos, Ah that's right. Every now and then I'm reminded that Elixir doesn't support currying when I try to do something haha Your suggestion makes sense. Would there be any downsides to having it, even if it isn't the most incredible function? Again to call on the `Function.identity/1`, and it's discussion, it's useful when it's useful for concise and semantic code. On Wednesday, 29 January 2020 22:43:51 UTC, Amos King - Binary Noggin wrote: Jesse, I see where you are going, but Elixir doesn't have currying. For instance, the last example you gave will return an error. You could make it work by changing it a bit. `@spec const(a) :: fn(any() -> a) when a: var` So, const would return an fn instead of taking two arguments. I don't know how useful that would be in the long run. I know it is common in function programming, but I don't see it being extremely helpful in Elixir. I'm ready to be convinced. Cheers, Amos King CEO Binary Noggin http://binarynoggin.com #business https://elixiroutlaws.com #elixir podcast http://thisagilelife.com #podcast ======================================================= I welcome VSRE emails. Learn more at http://vsre.info/ ======================================================= On Wed, Jan 29, 2020 at 4:01 PM Jesse Claven <jesse...@gmail.com> wrote: Hey everyone! I propose adding `Function.const/2` as a function which for argument `x`, would always return `x`. ``` @spec const(any(), any()) :: any() def const(_original_value, new_value), do: new_value ``` This is somewhat similar to the new `Function.identity/1` in that it may seem like we've easily lived without it, but it does afford some more concise/semantic ways to represent a common pattern. ``` fn _ -> something_else() end ``` This would become: ``` const(something_else()) ``` ``` Enum.map([0,1,2,3], &Function.const/2) ``` I'm new to Elixir, so I'm not sure of the weight that the name `const` would carry, so there could be a more acceptable name. If accepted, I'd be happy to create a PR! Equivalents in other languages: - Haskell: https://hackage.haskell.org/package/base-4.12.0.0/docs/Data-Function.html#v:const - PureScript: https://pursuit.purescript.org/packages/purescript-const/4.1.0/docs/Data.Const - Elm: https://package.elm-lang.org/packages/elm/core/latest/Basics#always - Scala: https://www.scala-lang.org/api/current/scala/Function$.html#const[T,U](x:T)(y:U):T - Idris: https://www.idris-lang.org/docs/current/prelude_doc/docs/Prelude.Basics.html#Prelude.Basics.const Thanks for your time. -- You received this message because you are subscribed to the Google Groups "elixir-lang-core" group. To unsubscribe from this group and stop receiving emails from it, send an email to elixir-l...@googlegroups.com. 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