[Haskell-cafe] Python is lazier than Haskell

Dan Doel dan.doel at gmail.com
Thu Apr 28 22:18:53 CEST 2011

(Sorry if you get this twice, Ertugrul; and if I reply to top. I'm
stuck with the gmail interface and I'm not used to it.)

On Thu, Apr 28, 2011 at 11:27 AM, Ertugrul Soeylemez <es at ertes.de> wrote:
> I don't see any problem with this.  Although I usually have a bottom-up
> approach, so I don't do this too often, it doesn't hurt, when I have to.

I do. It's low tech and inconvenient.

Whenever I program in Haskell, I miss Agda's editing features, where I
can write:

   foo : Signature
   foo x y z = ?

Then compile the file. The ? stands in for a term of any type, and
becomes a 'hole' in my code. The editing environment will then tell me
what type of term I have to fill into the hole, and give me
information on what is available in the scope. Then I can write:

   foo x y z = { partialImpl ? ? }

and execute another command. The compiler will make sure that
'partialImpl ? ?' has the right type to fill in the hole (with ?s
again standing in for terms of arbitrary type). If the type checking
goes through, it expands into:

   foo x y z = partialImpl { } { }

and the process repeats until my function is completely written. And
of course, let's not forget the command for automatically going from:

   foo x y z = { x }


   foo Con1 y z = { }
   foo Con2 y z = { }
   foo Con3 y z = { }

I don't think there's anything particularly Agda-specific to the
above. In fact, the inference required should be easier with
Haskell/GHC. Features like this would be pretty killer to have for
Haskell development; then I wouldn't have to prototype in Agda. :)

-- Dan

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