On Wednesday 20 April 2011 11:43:08, larry.liuxinyu wrote:
Hi,
I found there is similar question as: http://groups.google.com/group/haskell-cafe/browse_thread/thread/7439262 e9ac80dd2/91ca18e11ff00649?lnk=gst&q=QuickCheck+Ord+a#91ca18e11ff00649
I am still think it's very strange. For example:
prop_foo :: (Ord a) => [a] -> Property prop_foo xs = not (null xs) ==> maximum xs == minimum xs
This is an extreme case that the property is always wrong.
Not always, replicate n x has this property.
However, QuickCheck produces: *Main> test prop_foo OK, passed 100 tests.
This works at least, However, since 'a'<'b', they are order-able, what if I want to test prop_foo works for char?
ghci> test (prop_foo :: [Char] -> Property) You have to determine the type, by an explicit signature or by context.