Nondeterminism

This provides nondeterministic computations in Haskell. It implements an Amb monad in which you can perform nondeterministic choices along with a monad transformer version, AmbT.

Amb

An example which finds Pythagorean triplets up to a certain size, project Euler problem 9.

import Control.Monad
import Control.Monad.Amb
pyTriple :: (Num t, Ord t) => t -> Amb r (t, t, t)
pyTriple n = do a <- anIntegerBetween 1 n
                b <- anIntegerBetween (a + 1) n
                c <- anIntegerBetween (b + 1) n
                when (a*a + b*b /= c*c) fail'
                return (a,b,c)

length $ allValues $ pyTriple 10000

Future

• Docs!