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I need a function with following attributes.
(c->d)->(a->b->c)->a->b->d
my function:
funktionD = (.) . (.)
but :t funktionD
funktionD :: (a -> b) -> (c -> d -> a) -> c -> d -> b
ist this equal?
It is. Type variables–written in lowercase–are just that, variables. You can rename them all you like as long as the pattern of which are the same variable stays the same.
Furthermore, for essentially the same reason, for the type signature you gave there is only one possible function of that type (excluding functions that crash or go into infinite loops, that is). Something to think about!