[mcguire]

PowerShell? That's a new one....

I haven't used Idris, but as a proof assistant, Coq is one of the best computer games I know[1]. As a programming language, it's a very good proof assistant.[2]

[1] Really! It's fun. I've found the resulting proofs impossible to read, though. The closest description I can make is that they're programs for a stack machine; reading those is not a skill I've developed.

[2] All of the dependently typed languages, like Coq, that I've seen have not been very good programming languages, in my opinion. Except for ATS, which I don't think is a good programming language for different reasons. But I really like it, anyway.

[lmm]

> All of the dependently typed languages, like Coq, that I've seen have not been very good programming languages, in my opinion.

Yeah, that's why I'm looking at Idris - it seems like the only one that's oriented towards practical programming. I did eventually get it installed, but it's tough going doing anything with it when you don't know Haskell tbh.

[codygman]

> Idris - it seems like the only one that's oriented towards practical programming

Whether you like ATS or not, it's very oriented towards practical programming. Also, ATS mostly looks bad IMO because of the style the author uses.

I still haven't fully formed an opinion on ATS though. Idris does seem really cool and stuff like enforcing time/space usage through the type system excites me.

[mcguire]

I'm not sure whether my issue with ATS is the style of the author or its type system, although I suspect the former.

ATS is based on ML (the author started with Dependent ML), but the code has a very imperative feel, leading to statements like "let () = expr() in ..." and "let x = ... in ()".

The stuff at http://www.ats-lang.org/Examples.html is just hideous, by the way.

[codygman]

I agree with you, though I think it is because of the authors style. Check out some of Chris Done's ats code examples in a more appealing style:

https://gist.github.com/chrisdone/c23251e8b975dc805876

[codygman]

Here's just a small translation of the ats examples[0] page.

----------------- Copying File ----------------

Authors version:

    fun
    fcopy (
      inp: FILEref
    , out: FILEref
    ) : void = let
      val c = fileref_getc (inp)
    in
      if c >= 0 then let
        val () = fileref_putc (out, c) in fcopy (inp, out)
      end // end of [if]
    end (* end of [fcopy] *)

----------------- Naieve Fibonacci ----------------

My version:

    fun fcopy ( 
      inp: FILEref,
      out: FILEref
    ) : void = let
      val c = fileref_getc (inp)
    in
      if c >= 0 then let
        val () = fileref_putc (out, c) in fcopy (inp, out)
      end 
    end 

Authors version:

    fun
    fib (
      n: int
    ) : int =
      if n >= 2 then fib (n-2) + fib (n-1) else n

My Version (not sure if valid!):

    fun fib ( n: int ) : 
      int = if n >= 2 then fib (n-2) + fib (n-1) else n

----------------- Fast Fibonacci ----------------

Authors Version:

    fun
    fibc (
      n: int
    ) : int = let
      fun loop (n: int, f0: int, f1: int) =
        if n > 0 then loop (n-1, f1, f0+f1) else f0
      // end of [loop]
    in
      loop (n, 0, 1)
    end // end of [fibc]

My Version:

    fun fibc ( n: int ) : int = 
      let
        fun loop (n: int, f0: int, f1: int) =
          if n > 0 then loop (n-1, f1, f0+f1) else f0
      in
      loop (n, 0, 1)
    end

0: http://www.ats-lang.org/Examples.html