#3919: Or-patterns as GHC extension -------------------------------------+------------------------------------- Reporter: BjornEdstrom | Owner: Type: feature request | Status: new Priority: normal | Milestone: ⊥ Component: Compiler | Version: Resolution: | Keywords: Operating System: Unknown/Multiple | Architecture: | Unknown/Multiple Type of failure: None/Unknown | Test Case: Blocked By: | Blocking: Related Tickets: | Differential Rev(s): Wiki Page: | -------------------------------------+------------------------------------- Comment (by osa1): Good point. I think we may require parens around or patterns. So the parsing rule would be like: {{{ pat ::= '(' or-pattern-or-pat ')' | ... (where none of the productions accept '|') or-pattern-or-pat ::= pat '|' or-pattern-or-pat | pat }}} I personally dislike messier syntax like `:|` and `:|:`, because I'm hoping to use this syntax instead of `_` patterns, and I may need to chain a lot of constructors. {{{ f (T1 ...) = ... f (T2{} | T3{} | T4{}) = ... }}} vs {{{ f (T1 ...) = ... f (T2{} :|: T3{} :|: T4{}) = ... }}} Second one looks really bad IMHO. In addition, `:|:` is a valid operator syntax, but `|` is a reserved operator. -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/3919#comment:18 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler