[Haskell] Announcing Djinn, version 2004-12-11, a coding wizard

[Donald Bruce Stewart]

lennart:
> Howdy, y'all!
> 
> I've written a small program that takes a (Haskell) type
> and gives you back a function of that type if one exists.
> It's kind of fun, so I thought I'd share it.
> 
> It's probably best explained with a sample session.
> 
>   calvin% djinn
>   Welcome to Djinn version 2005-12-11.
>   Type :h to get help.
> # Djinn is interactive if not given any arguments.
> # Let's see if it can find the identity function.
>   Djinn> f ? a->a
>   f :: a -> a
>   f x1 = x1
> # Yes, that was easy.  Let's try some tuple munging.
>   Djinn> sel ? ((a,b),(c,d)) -> (b,c)
>   sel :: ((a, b), (c, d)) -> (b, c)
>   sel ((_, v5), (v6, _)) = (v5, v6)

I've written a little plugin to use Djinn from lambdabot. You
can interact with it on the #haskell irc channel *right now* 

Transcript: 

    15:39:01 <dons> @djinn a -> b -> a
    15:39:02 <lambdabot> x :: a -> b -> a
    15:39:02 <lambdabot> x x1 _ = x1
    15:39:11 <dons> @djinn (a -> b -> c) -> ((a,b) -> c)
    15:39:11 <lambdabot> x :: (a -> b -> c) -> (a, b) -> c
    15:39:11 <lambdabot> x x1 (v3, v4) = x1 v3 v4
    15:39:27 <dons> @djinn (a -> b) -> (c -> b) -> Either a c -> b
    15:39:27 <lambdabot> x :: (a -> b) -> (c -> b) -> Either a c -> b
    15:39:27 <lambdabot> x x1 x2 x3 = case x3 of
    15:39:27 <lambdabot>      Left l4 -> x1 l4
    15:39:27 <lambdabot>      Right r5 -> x2 r5
    15:40:06 <xerox> @djinn a -> [a] -> [a]
    15:40:07 <lambdabot> x :: a -> [a] -> [a]
    15:40:07 <lambdabot> x _ x2 = x2
    15:40:08 <dons> @help djinn
    15:40:09 <lambdabot>  @djinn <type>
    15:40:09 <lambdabot> Generates Haskell code from a type.

And then we go crazy with @djinn for about 10 minutes :)

Great stuff Lennart.

Cheers,
   Don