Re: [Haskell-cafe] some ideas for Haskell', from Python

Yes, the Agda modules remind me of Cayenne. :) On Tue, Jan 20, 2009 at 12:54 PM, Bas van Dijk wrote:

On Wed, Jan 14, 2009 at 3:59 PM, Manlio Perillo wrote:

...

2) In Python it is possible to import modules inside a function.

In Haskell something like:

joinPath' root name = joinPath [root, name] importing System.FilePath (joinPath)

I just like to point out the dependently typed, Haskell-like, programming language Agda[1] which has a very nice module system with the following features:

* Modules can contain other modules

* Modules can be locally opened. For example: mapMaybe f m = let open Maybe in maybe nothing (just . f) m

* Renaming of important names: For example: open Maybe renaming (Maybe to option; nothing to none; just to some)

* Parameterized modules: For example:

module Sort (A : Set) (_<_ : A -> A -> Bool) where insert : A -> List A -> List A insert y [] = y :: [] insert y (x :: xs) with x < y ... | true = x :: insert y xs ... | false = y :: x :: xs

See section 2.7 of the following Agda tutorial (an open minded Haskell hacker should be able to read that section on its own):

http://www.cs.chalmers.se/~ulfn/darcs/AFP08/LectureNotes/AgdaIntro.pdf

Hopefully Haskell can borrow some of these ideas sometime.

regards,

Bas

[1] http://wiki.portal.chalmers.se/agda/ _______________________________________________ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe