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POHow to falsify commutativity of function composition with QuickCheck
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  1. POHow to falsify commutativity of function composition with QuickCheck
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    copied!<ol> <li><p>What is ex that should be pass to CoArbitrary of the following code?</p></li> <li><p>How to use Function in Test.QuickCheck.Function to represent f and g in proposition?</p></li> <li><p>is it correct to write , if not, how?</p> <p>where types = [f, g] :: [Function] </p></li> <li><p>Can variant accept Function ? as i know generate function often use >&lt; or variant which stated in the source code of QuickCheck</p></li> </ol> <p>The error:</p> <pre><code>&lt;interactive&gt;:1:12: No instance for (Eq (b0 -&gt; b0)) arising from a use of `prop_commutative' Possible fix: add an instance declaration for (Eq (b0 -&gt; b0)) In the first argument of `quickCheck', namely `prop_commutative' In the expression: quickCheck prop_commutative In an equation for `it': it = quickCheck prop_commutative </code></pre> <p>[Updated] </p> <p>but it is not implemented CoArbitrary <a href="http://www.google.com.hk/url?sa=t&amp;rct=j&amp;q=QuickCheck+meiser.pdf&amp;source=web&amp;cd=1&amp;ved=0CBwQFjAA&amp;url=http%3A%2F%2Fwww.st.cs.uni-saarland.de%2Fedu%2Fseminare%2F2005%2Fadvanced-fp%2Fslides%2Fmeiser.pdf&amp;ei=hhfHTo_ZDdCciAethMjqDw&amp;usg=AFQjCNFF467CXacWGMkN8jvgqatkcLcVcg" rel="nofollow">http://www.google.com.hk/url?sa=t&amp;rct=j&amp;q=QuickCheck+meiser.pdf&amp;source=web&amp;cd=1&amp;ved=0CBwQFjAA&amp;url=http%3A%2F%2Fwww.st.cs.uni-saarland.de%2Fedu%2Fseminare%2F2005%2Fadvanced-fp%2Fslides%2Fmeiser.pdf&amp;ei=hhfHTo_ZDdCciAethMjqDw&amp;usg=AFQjCNFF467CXacWGMkN8jvgqatkcLcVcg</a></p> <p>Another writing mimic the example in Function, parse error at '=' in ghci <code>let prop_commutative (Fun _ f) (Fun _ g) = (f.g) == (g.f)</code> can run</p> <p>The code:</p> <pre><code>import Test.QuickCheck.Function import Test.QuickCheck.Gen import Test.QuickCheck let prop_commutative (Fun _ f) (Fun _ g) = (f.g) == (g.f) main = quickCheck prop_commutative </code></pre>
 

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