On Fri, Nov 16, 2012 at 7:10 AM, Daryoush Mehrtash <dmehrtash@gmail.com> wrote:

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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