Am Montag 06 April 2009 17:53:24 schrieb Paul Keir:

module Main where

data (:%^&) a b = a :%^& b deriving (Show)

main = do

print $ 18 :%^& (Just 99)

print $ (,) 9 10

print $ 9 , 10

The last line in the code above causes a compile error.

Why does infix use of the comma (tuple constructor?) function fail without brackets?

Tuples are special baked-in syntax. The parentheses are part of the tuple constructor(s). It may be confusing you that you can use it prefix as well as "aroundfix".

Thanks,

Paul

On Mon, Apr 6, 2009 at 8:53 AM, Paul Keir wrote:

module Main where

data (:%^&) a b = a :%^& b    deriving (Show)

main = do

  print $ 18 :%^& (Just 99)

  print $ (,) 9 10

  print $ 9 , 10

The last line in the code above causes a compile error.

Why does infix use of the comma (tuple constructor?) function fail without brackets?

Thanks,

Paul

When I want a lighter syntax for pairs (when doing a long list of them, e.g.), I often define (&) :: a -> b -> (a,b) a & b = (a,b) and then you can indeed write print $ 1 & 2 (assuming you get precedence right). Alex