[GHC] #5108: Allow unicode sub/superscript symbols in both identifiers and operators

[GHC]

#5108: Allow unicode sub/superscript symbols in both identifiers and operators
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    Reporter:  mikhail.vorozhtsov  |       Owner:                  
        Type:  feature request     |      Status:  patch           
    Priority:  normal              |   Milestone:  7.4.1           
   Component:  Compiler (Parser)   |     Version:  7.1             
    Keywords:  lexer unicode       |          Os:  Unknown/Multiple
Architecture:  Unknown/Multiple    |     Failure:  None/Unknown    
  Difficulty:  Unknown             |    Testcase:                  
   Blockedby:                      |    Blocking:                  
     Related:                      |  
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Changes (by simonmar):

  * difficulty:  => Unknown


Comment:

 I'm not keen on this patch for a few reasons:

  * It's inconsistent to allow superscript/subscript on symbols.  Haskell
    doesn't currently allow primes on symbols, for example.

  * The patch has a bunch of Unicode constants baked into it

  * It adds a bunch of extra tests to the inner loop.  I haven't
    measured it but I wouldn't be surprised if this slows down the lexer.

 Perhaps it might be better just to allow the category Lm (MODIFIER LETTER)
 as part of an identifier?  That would include all the primes and
 subscript/superscript things.

-- 
Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/5108#comment:4>
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