02 Oct 2001 15:16:27 +0300, Dmitry Astapov
I need to define SetsAsLists as an instance of Set by supplying definitions for all Set methods, but definitions I wrote led me to adding additional constraints on "union" and "memeber" methods.
What constraints? The class already says that these operations require Eq on the element type:
class Set s where empty :: s a isEmpty :: s a -> Bool singleton :: a -> s a union :: Eq a => s a -> s a -> s a ^^^^ member :: Eq a => a -> s a -> Bool ^^^^ choice :: s a -> (a, s a)
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