Infix declarations

Main.purs

module Main where

import Debug.Trace
 
data Two a b = Two a b

instance showTwo :: (Show a, Show b) => Show (Two a b) where
  show (Two x y) = "(" <> show x <> " : " <> show y <> ")"

-- Non-associative
(^^) = Two
infix  0 ^^

-- left-associative
(<<) = Two
infixl 0 <<

-- right-associative
(>>) = Two
infixr 0 >>

-- Precedence
(<<%) = Two
infixl 1 <<%

(<<%%) = Two
infixl 9 <<%%

(^^^) = Two

main = do
  trace "Declared left-associative"
  print (1 << 1 << 1 << 1 << 1 << 1)

  trace "Declared left-associative"
  print (1 >> 1 >> 1 >> 1 >> 1 >> 1)

  trace "Declared non-associative"
  print (1 ^^ 1 ^^ 1 ^^ 1 ^^ 1 ^^ 1)

  trace "Without a fixity declaration, it defaults to being left-associative"
  print (1 ^^^ 1 ^^^ 1 ^^^ 1 ^^^ 1 ^^^ 1)

  trace "Default precedence"
  print (1 ^^^ 1 << 1)
  print (1 << 1 ^^^ 1)
  print (1 ^^^ 1 << 1 ^^^ 1 << 1 ^^^ 1)

  print (1 <<% 1 <<%% 1)

output.txt

Declared left-associative
(((((1 : 1) : 1) : 1) : 1) : 1)
Declared left-associative
(1 : (1 : (1 : (1 : (1 : 1)))))
Declared non-associative
(((1 : 1) : (1 : 1)) : (1 : 1))
Without a fixity declaration, it defaults to being left-associative
(((((1 : 1) : 1) : 1) : 1) : 1)
Default precedence
(1 : (1 : 1))
((1 : 1) : 1)
(((1 : (1 : 1)) : (1 : 1)) : 1)
(1 : (1 : 1))