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Early versions of this type system had problems with equality
What's the type of ==?
Something like a -> a -> Bool
Except that a must not be a function type
Haskell solves this problem:
(Eq a) => a -> a -> Bool
And function types are not instances of Eq
Similarly, ordered types should be declared instances of Ord
Values can be compared with <, >, etc.
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Copyright © 1999,2008 Mark Dominus |