Re: [Haskell-cafe] List Monads and non-determinism

2013-07-20 Thread Alberto G. Corona
Matt It is not return, but the bind the one that does the miracle of multiplication. By its definition for the list monad, it applies the second term once for each element are in the first term. So return is called many times. At the end, bind concat all the small lists generated 2013/7/20 Matt

[Haskell-cafe] Default installation path of haskell platform in windows

2013-07-20 Thread Ivan Perez
Hi café, I just spent the whole day fighting ghc and cabal to get my program compiled in windows (and I haven't succeeded yet :) ) realgcc is not very happy about paths with spaces in them (I think there's an open bug about the way ghc calls realgcc, which manifests if you use extra-lib-dirs in t

Re: [Haskell-cafe] Proposal: Non-recursive let

2013-07-20 Thread Evan Laforge
On Tue, Jul 16, 2013 at 5:20 PM, Richard A. O'Keefe wrote: > Brian Marick sent me a couple of his stickers. > The one I have on my door reads "to be less wrong than yesterday". > The other one I keep free to bring out and wave around: > > "An example would be handy about now." Just by coi

Re: [Haskell-cafe] Dynamic and equality

2013-07-20 Thread adam vogt
On Sat, Jul 20, 2013 at 12:31 AM, Carter Schonwald wrote: > the tricky part then is to add support for other types. > > another approach to existentially package type classes with the data type! > > eg > data HasEq = forall a . HasEq ( Eq a => a) > or its siblinng > data HasEq a = Haseq (Eq a =>

Re: [Haskell-cafe] Wrapping all fields of a data type in e.g. Maybe

2013-07-20 Thread adam vogt
On Sat, Jul 20, 2013 at 12:14 AM, Michael Orlitzky wrote: > For posterity, I report failure =) Hi Michael, It's fairly straightforward to generate the new data with template haskell [1], and on the same page, section "10.7 'generic' zipWith" is likely to be similar to your merging code. [1]

Re: [Haskell-cafe] List Monads and non-determinism

2013-07-20 Thread Eric Rasmussen
For the sake of approaching this in yet another way, it can also be helpful to substitute the definitions of bind and return in your expression. If we start with the definitions: instance Monad [] where xs >>= f = concat (map f xs) return x = [x] Then we can make the following transformations

Re: [Haskell-cafe] HaskellWiki images disappeared

2013-07-20 Thread Thomas Schilling
Should be fixed now. The wiki was recently transferred to a new server and this got unfortunately broken in the process. On 18 Jul 2013 22:45, "Henk-Jan van Tuyl" wrote: > > > L.S., > > It looks like the HaskellWiki images have disappeared; can anybody repair > this? (See for example http://www.h

[Haskell-cafe] ANN: darcsden 1.1 released, darcs hub news 2013/07

2013-07-20 Thread Simon Michael
Hi all, here is a combined darcsden and darcs hub update. darcsden 1.1 released = darcsden 1.1 is now available on hackage! This is the updated version of darcsden which runs hub.darcs.net, so these changes are also relevant to that site's users. (More darcs hub news below.)

[Haskell-cafe] ANN: data-fin

2013-07-20 Thread wren ng thornton
-- data-fin 0.1.0 The data-fin package offers the family of totally ordered finite sets, implemented as newtypes of Integer, etc. Thus, you get all the joys of: data Nat = Zero | Succ !Nat data Fin

Re: [Haskell-cafe] Dynamic and equality

2013-07-20 Thread Alberto G. Corona
You can define: data EqDyn= forall a.(Typeable a, Eq a)=> EqDyn a instance Eq EqDyn where (EqDyn x) == (EqDyn y)= typeOf x== typeOf y && x== unsafeCoerce y unsafeCoerce is safe synce the expression assures that types are equal 2013/7/20 adam vogt > On Sat, Jul 20, 2013 at 12:31 AM, Carte