I think this is the monomorphism restriction, you can see more details
on the web page:
http://www.haskell.org/hawiki/MonomorphismRestriction
On 3/30/06, David Laffin
Hi,
Newbie question. Given the inferred type for square, the inferred types for quad1, quad2 and quad3 are what I would expect. Is there a straightforward explanation (i.e. one that a newbie would understand) as to why the inferred type for quad4 is less general?
Regards, dl
-- GHC Interactive, version 6.4, for Haskell 98.
Prelude> let square x = x * x Prelude> :t square square :: (Num a) => a -> a
Prelude> let quad1 x = square (square x) Prelude> :t quad1 quad1 :: (Num a) => a -> a
Prelude> let quad2 x = square $ square x Prelude> :t quad2 quad2 :: (Num a) => a -> a
Prelude> let quad3 x = (square . square) x Prelude> :t quad3 quad3 :: (Num a) => a -> a
Prelude> let quad4 = square . square Prelude> :t quad4 quad4 :: Integer -> Integer
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