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{-|
Module : Test.VeriFuzz.Graph.Random
Description : Random generation for DAG
Copyright : (c) Yann Herklotz Grave 2018
License : GPL-3
Maintainer : ymherklotz@gmail.com
Stability : experimental
Portability : POSIX
Define the random generation for the directed acyclic graph.
-}
module Test.VeriFuzz.Graph.Random where
import Data.Graph.Inductive (Graph, LEdge, mkGraph)
import Test.QuickCheck (Arbitrary, Gen, arbitrary, generate,
infiniteListOf, resize, suchThat)
-- | Gen instance to create an arbitrary edge, where the edges are limited by
-- `n` that is passed to it.
arbitraryEdge :: (Arbitrary e) => Int -> Gen (LEdge e)
arbitraryEdge n = do
x <- with $ \a -> a < n && a > 0 && a /= n-1
y <- with $ \a -> x < a && a < n && a > 0
z <- arbitrary
return (x, y, z)
where
with = suchThat . resize n $ arbitrary
-- | Gen instance for a random acyclic DAG.
randomDAG :: (Arbitrary l, Arbitrary e, Graph gr)
=> Int -- ^ The number of nodes
-> Gen (gr l e) -- ^ The generated graph. It uses Arbitrary to
-- generate random instances of each node
randomDAG n = do
list <- infiniteListOf arbitrary
l <- infiniteListOf $ arbitraryEdge n
return . mkGraph (nodes list) $ take (10*n) l
where
nodes l = zip [0..n] $ take n l
-- | Generate a random acyclic DAG with an IO instance.
genRandomDAG :: (Arbitrary l, Arbitrary e, Graph gr)
=> Int
-> IO (gr l e)
genRandomDAG = generate . randomDAG
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