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Vladislav Zavialov authoredThis patch implements a part of GHC Proposal #229 that covers five operators: * the bang operator (!) * the tilde operator (~) * the at operator (@) * the dollar operator ($) * the double dollar operator ($$) Based on surrounding whitespace, these operators are disambiguated into bang patterns, lazy patterns, strictness annotations, type applications, splices, and typed splices. This patch doesn't cover the (-) operator or the -Woperator-whitespace warning, which are left as future work.
Vladislav Zavialov authoredThis patch implements a part of GHC Proposal #229 that covers five operators: * the bang operator (!) * the tilde operator (~) * the at operator (@) * the dollar operator ($) * the double dollar operator ($$) Based on surrounding whitespace, these operators are disambiguated into bang patterns, lazy patterns, strictness annotations, type applications, splices, and typed splices. This patch doesn't cover the (-) operator or the -Woperator-whitespace warning, which are left as future work.
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proposal-229e.hs 474 B
{-# LANGUAGE BangPatterns #-}
module Proposal229e ((!), f) where
(!) :: Maybe a -> a -> (a, a)
f :: a -> a
-- the preceding '}' is not from a comment,
-- so (!) is tight infix (therefore an operator)
Nothing{}!x = (x, x)
-- the following '{' opens a multi-line comment,
-- so (!) is loose infix (therefore an operator)
Just a !{-comment-}x = (a, x)
-- the preceding '}' is closing a multi-line comment,
-- so (!) is prefix (therefore a bang pattern)
f{-comment-}!x = x