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{-# OPTIONS_GHC -fno-warn-orphans #-}
{-# LANGUAGE FlexibleInstances #-}
{- |
Module : Data.GraphViz.Testing.Instances.FGL
Description : 'Arbitrary' instances for FGL graphs.
Copyright : (c) Ivan Lazar Miljenovic
License : 3-Clause BSD-style
Maintainer : Ivan.Miljenovic@gmail.com
This module defines the 'Arbitrary' instances for FGL 'DynGraph'
graphs. Note that this instance cannot be in
"Data.GraphViz.Testing.Instances", as this instance requires the
FlexibleInstances extension, which makes some of the other
'Arbitrary' instances fail to type-check.
-}
module Data.GraphViz.Testing.Instances.FGL() where
import Test.QuickCheck
import Data.GraphViz.Internal.Util (uniq)
import Control.Monad (liftM, liftM3)
import Data.Function (on)
import Data.Graph.Inductive.Graph (Graph, delNode, mkGraph, nodes)
import Data.List (sortBy)
-- -----------------------------------------------------------------------------
-- Arbitrary instance for FGL graphs.
instance (Graph g, Arbitrary n, Arbitrary e) => Arbitrary (g n e) where
arbitrary = do ns <- suchThat genNs (not . null)
let nGen = elements ns
lns <- mapM makeLNode ns
les <- liftM (sortBy (compare `on` toE)) . listOf
$ makeLEdge nGen
return $ mkGraph lns les
where
genNs = liftM uniq arbitrary
toE (f,t,_) = (f,t)
makeLNode n = liftM ((,) n) arbitrary
makeLEdge nGen = liftM3 (,,) nGen nGen arbitrary
shrink gr = case nodes gr of
-- Need to have at least 2 nodes before we delete one!
ns@(_:_:_) -> map (`delNode` gr) ns
_ -> []
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