# [Haskell-cafe] need help with understanding expression

Daryoush Mehrtash dmehrtash at gmail.com
Fri Nov 16 08:10:54 CET 2012

```I am having hard time understanding how removing the  outer parenthesis in

(max.(+1)) 2 2

to

max.(+1) 2 2

changes the meaning of expression.

My expectation was that "max.(+1) takes two numbers and returns the max as
defined in the type:

:t max.(+1)
max.(+1) :: (Ord b, Num b) => b -> b -> b

With parenthesis it does what I expect it to:

Prelude> :t (max.(+1)) 2 2
(max.(+1)) 2 2 :: (Ord b, Num b) => b
Prelude>  (max.(+1)) 2 2
3

But if I remove the parenthesis I get a beast that I have no idea what its
type signature mean any more

Prelude> :t (max.(+1)) 2 2
(max.(+1)) 2 2 :: (Ord b, Num b) => b
Prelude> :t max.(+1) 2 2
max.(+1) 2 2 :: (Ord b, Num a1, Num (a1 -> a -> b)) => a -> b -> b

How did removal of parenthesis changed the meaning?      How do you
interpret the type:  "(Ord b, Num a1, Num (a1 -> a -> b)) => a -> b -> b"?

Thanks

--
Daryoush

Weblog:  http://onfp.blogspot.com/
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