# nondeterminism: A monad and monad transformer for nondeterministic computations.

[ ai, constraints, control, failure, library, monads ] [ Propose Tags ]

Nondeterministic computations

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Versions [RSS] 1.0, 1.2, 1.4, 1.5 base (>=3 && <5), containers, mtl (>=2) [details] LicenseRef-LGPL Andrei Barbu Andrei Barbu Control, AI, Constraints, Failure, Monads head: git clone http://github.com/abarbu/nondeterminism-haskell by AndreiBarbu at 2022-05-20T01:00:52Z LTSHaskell:1.5, NixOS:1.5, Stackage:1.5 2 direct, 0 indirect [details] 2986 total (33 in the last 30 days) 2.0 (votes: 1) [estimated by Bayesian average] λ λ λ Docs available Last success reported on 2022-05-20

## Readme for nondeterminism-1.5

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# Nondeterminism

This package is available via Hackage where its documentation resides.

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
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) empty
return (a,b,c)
length $allValues$ pyTriple 100


More examples can be found in tests/test.hs.

## Future

• allValues is not lazy in its return value