Hi,
I've run into a small problem whilst doing some manual type checking, to see
if I could match the results given by hugs
prelude :t foldr filter
foldr filter :: [a] - [a - Bool] - [a]
-- This was fine and was the same as my answer, so I tested it with
prelude foldr filter [1,2,3,4] [even,odd]
-- and the answer was indeed an empty list
-- However I got stuck when attempting to derive the result of
map (foldr filter)
-- Hugs says that:
prelude :t map (foldr filter)
map (foldr filter) :: [[a]] - [[a - Bool] - [a]]
Two main questions:
1/ How does hugs derive this answer?
2/ What input can I give so that it yields a correct result? I've tried
giving it a list of lists but it fails...
Any pointers would be greatly appreciated!
Many Thanks,
Lee
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