Why are brackets required to print type information of .?

Question

To print the type information of . I use :

λ> :type (.)
(.) :: (b -> c) -> (a -> b) -> a -> c

If I omit the brackets , causes an error :

λ> :type .
<interactive>:1:1: parse error on input ‘.’

The same is not true for other types :

λ> :type 1
1 :: Num a => a
λ> :type (1)
(1) :: Num a => a
λ> :type True 
True :: Bool
λ> :type (True)
(True) :: Bool

Why the special behavior for . ?

Answer 1

. without the parentheses only works in infix position. :t however takes an expression, e.g. a function, and to turn an infix operator symbol into an expression, you need to surround it with parens.

Consider:

3 + 4 = (+) 3 4  -- pseudocode

and

myPlus = (+)

which is the same as

myPlus a b = a + b
myPlus a b = (+) a b

And it applies equally to all other infix operators such as * or >>= or &&& etc.