nondeterminism

A monad and monad transformer for nondeterministic computations.

Version on this page:1.4
LTS Haskell 24.16:1.5
Stackage Nightly 2025-10-24:1.5
Latest on Hackage:1.5

See all snapshots nondeterminism appears in

LicenseRef-LGPL licensed and maintained by Andrei Barbu
This version can be pinned in stack with:nondeterminism-1.4@sha256:56598728aff2900c8b1d0002c1bd35420bc25289db094b73fdbfd33ddce8f8a9,1032

Module documentation for 1.4

Depends on 3 packages(full list with versions):
base, containers, mtl
Used by 1 package in nightly-2017-12-10(full list with versions):
csp

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
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) 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