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J.A. Alonso

A tour of the Haskell monad functions - 1 views

members.chello.nl/...tourdemonad.html

Tutorial Haskell

shared by J.A. Alonso on 24 Jan 10 - Cached
  • ap module: Control.Monad type: ap :: (Monad m) => m (a -> b) -> m a -> m b
Javier Neira

Monads in 15 minutes: Backtracking and Maybe - 0 views

www.randomhacks.net/...monads-in-15-minutes

monads haskell backtracking howto

shared by Javier Neira on 09 Nov 09 - Cached
  • type Choice a = [a] choose :: [a] -> Choice a choose xs = xs
  • Because Haskell doesn’t compute answers until we ask for them, we get the actual backtracking for free!
  • The missing function is almost too trivial to mention: Given a single value of type a, we need a convenient way to construct a value of type Choice a:
  • ...5 more annotations...
  • More math trivia: return is also known as unit and η. That’s a lot of names for a very simple idea.)
  • makePairs = choose [1,2,3] >>= (\x -> choose [4,5,6] >>= (\y -> return (x,y)))
  • makePairs' = do x <- choose [1,2,3] y <- choose [4,5,6] return (x,y)
  • Every monad has three pieces: return, map and join.
  • Backtracking: The lazy way to code
Xiaobin Huang

'Cannot justify constraints in explicitly typed binding ', Hugs complained. - 10 views

Now I know, it should be 'permutation :: Eq a => [a]->[[a]]'. Xiaobin Huang wrote: > hi all, > > I'm new to Haskell. > > I wrote a permutation prog. > > permutation [] = [[]] > p...

started by Xiaobin Huang on 14 Nov 08 1 follow-up, last by Xiaobin Huang on 16 Nov 08
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