"be consistent" | |
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Re^2: RFC: A Perlesque Introduction to Haskell, Part One (draft)by FoxtrotUniform (Prior) |
on Jun 23, 2004 at 22:26 UTC ( [id://369194]=note: print w/replies, xml ) | Need Help?? |
What you call extensionality is what I've known as currying. Then I should do a better job. Extensionality says that the following two definitions are equivalent: The reason this works is that xs is free on both sides of bar: it's basically a placeholder that says "a list should go here". Both of these functions have type (a -> a) -> [a] -> a (modulo monomorphism-restriction annoyances). On the other hand, the function application is a curried expression: while foldl f xs returns a scalar, foldl f returns a function from lists to scalars. To me, currying means partial function application, and it's useful for producing ad-hoc functions where lambda is overkill. I like your point that currying is easier to understand when you know about type signatures, and thanks for the link to MJD's talk. --
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