#7627: Space in nullary unboxed tuples ---------------------------------+------------------------------------------ Reporter: monoidal | Owner: Type: bug | Status: patch Priority: normal | Milestone: Component: Compiler | Version: 7.6.1 Keywords: | Os: Unknown/Multiple Architecture: Unknown/Multiple | Failure: None/Unknown Difficulty: Unknown | Testcase: Blockedby: | Blocking: Related: | ---------------------------------+------------------------------------------ Changes (by simonpj): * difficulty: => Unknown Comment: I agree that this is a tiresome issue, but I'm not convinced that adding spaces is the right way to go. What is the name of the type constructor? Presumably "`(##)`". We don't have ANY type constructors that have spaces in the middle of their names. An alternative is to permit "`(##)`" to parse as a type and a term, just as `()` does. The only reason it does not at the moment is becuase if you had an operator "`##`", then "`(##)`" would usually be the parenthesised version of it. The lexer has a special check: {{{ <0> { "(#" / { ifExtension unboxedTuplesEnabled `alexAndPred` notFollowedBySymbol } { token IToubxparen } "#)" / { ifExtension unboxedTuplesEnabled } { token ITcubxparen } } }}} Notice that `notFollowedBySymbol` thing. That's what stops "`(##)`" lexing as "`(#`" followed by "`#)`". I think. So we could just back off this and say that if you have `-XUboxedTuples` then "`(##)`" means a unit unboxed tuple, not the operator "`##`". I think that'd be better. What about "`(#-)`"? Maybe that should parse as the parenthesised operator "`#-`". So the lexer would essentialy have to recognise "`(##)`" and do the right thing (two lexemes). Simon M, or anyone else, any opinions? Simon -- Ticket URL: http://hackage.haskell.org/trac/ghc/ticket/7627#comment:3 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler

#7627: Space in nullary unboxed tuples ---------------------------------+------------------------------------------ Reporter: monoidal | Owner: Type: bug | Status: patch Priority: normal | Milestone: 7.8.1 Component: Compiler | Version: 7.6.1 Keywords: | Os: Unknown/Multiple Architecture: Unknown/Multiple | Failure: None/Unknown Difficulty: Unknown | Testcase: Blockedby: | Blocking: Related: | ---------------------------------+------------------------------------------ Comment(by igloo): Sounds like the right thing to me, too. I'm not sure what the best way to implement it is, though. Perhaps have a single token for `(##)` and tell the parser what it means? Incidentally, HEAD seems to have the unwanted space now: {{{ Prelude> :t (# #) (# #) :: (# #) }}} and `:i` can't understand the unboxed unit tuple, although it does work for others: {{{ Prelude> :i (##) Top level: Not in scope: `##' Prelude> :i (# #) <interactive>:1:3: parse error (possibly incorrect indentation or mismatched brackets) Prelude> :i (#,#) data (#,#) a b = (#,#) a b -- Defined in `GHC.Prim' }}} -- Ticket URL: http://hackage.haskell.org/trac/ghc/ticket/7627#comment:5 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler

#7627: Space in nullary unboxed tuples ---------------------------------+------------------------------------------ Reporter: monoidal | Owner: igloo Type: bug | Status: patch Priority: normal | Milestone: 7.8.1 Component: Compiler | Version: 7.6.1 Keywords: | Os: Unknown/Multiple Architecture: Unknown/Multiple | Failure: None/Unknown Difficulty: Unknown | Testcase: Blockedby: | Blocking: Related: | ---------------------------------+------------------------------------------ Comment(by ian@…): commit 20b98f350d7b30118ca311117903fc039f6b85ce {{{ Author: Ian Lynagh Date: Mon Feb 25 19:02:57 2013 +0000 Change how unboxed tuples are lexed; fixes #7627 (# is now always a lexeme, even if followed by a symbol. compiler/parser/Lexer.x | 2 +- docs/users_guide/glasgow_exts.xml | 8 ++++++++ 2 files changed, 9 insertions(+), 1 deletions(-) }}} -- Ticket URL: http://hackage.haskell.org/trac/ghc/ticket/7627#comment:7 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler