8 Jan
2011
8 Jan
'11
4:45 p.m.
Tangential to the discussion, there is a nice idiom for using an alternative typeclass that works well in the Quickcheck case: newtypes. For example, if I have a test function: testString :: String -> Bool testString s = f1 s == f2 s and the default instance of String isn't doing what I want, I could define a custom arbitrary method: testString = do s <- myArbitraryStr return (f1 s == f2 s) But I could also newtype String, define an instance for that newtype, and use either of these (in my opinion) nice alternative spellings: testString (MyString s) = ... testString = do MyString s <- arbitrary I especially like the first form. Cheers, Edward