[GHC] #4148: improve new recursive do syntax

[GHC]

#4148: improve new recursive do syntax
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    Reporter:  guest             |       Owner:                  
        Type:  feature request   |      Status:  patch           
    Priority:  low               |   Milestone:  7.6.1           
   Component:  Compiler          |     Version:  6.12.3          
    Keywords:                    |          Os:  Unknown/Multiple
Architecture:  Unknown/Multiple  |     Failure:  None/Unknown    
  Difficulty:  Unknown           |    Testcase:                  
   Blockedby:                    |    Blocking:                  
     Related:                    |  
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Comment(by simonpj@…):

 commit 4f8e86b44ecc31056d0bd7af325b9bb239ddf7a0
 {{{
 Author: Simon Peyton Jones <simonpj at microsoft.com>
 Date:   Tue Jun 12 08:42:36 2012 +0100

     Revive 'mdo' expressions, per discussion in Trac #4148

     Summary:
       - mdo expressions are enabled by RecursiveDo pragma

       - mdo expressions perform full segmentation

       - 'rec' groups inside 'do' are changed so they do *not*
         perform any segmentation.

       - Both 'mdo' and 'rec' are enabled by 'RecursiveDo'
         'DoRec' is deprecated in favour of 'RecursiveDo'
         (The 'rec' keyword is also enabled by 'Arrows', as now.)

     Thanks to Levent for doing all the work

  compiler/main/DynFlags.hs         |    9 +-
  compiler/parser/Lexer.x           |    7 +-
  compiler/rename/RnExpr.lhs        |   25 +++--
  docs/comm/genesis/modules.html    |    2 +-
  docs/users_guide/flags.xml        |    8 +-
  docs/users_guide/glasgow_exts.xml |  264
 +++++++++++++++++++++---------------
  6 files changed, 178 insertions(+), 137 deletions(-)
 }}}

-- 
Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/4148#comment:33>
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