group keyword with TransformListComp

Simon Peyton-Jones simonpj at microsoft.com
Tue Jun 23 11:12:18 EDT 2009


I don't mind what keyword (or indeed syntax) we use!  Better alternatives welcome.

Simon

| -----Original Message-----
| From: glasgow-haskell-users-bounces at haskell.org [mailto:glasgow-haskell-users-
| bounces at haskell.org] On Behalf Of Neil Mitchell
| Sent: 21 June 2009 19:15
| To: glasgow-haskell-users at haskell.org; Max Bolingbroke
| Subject: group keyword with TransformListComp
| 
| Hi,
| 
| The TransformListComp extension makes group a keyword. Unfortunately
| group is a useful function, and is even in Data.List. Thus,
| Data.List.group and TransformListComp are incompatible. This seems a
| very painful concession to give up a nice function name for a new
| extension. Is this intentional? Here's an example:
| 
| > $ cat GroupKeyword.hs
| > {-# LANGUAGE TransformListComp #-}
| > module GroupKeyword where
| >
| > a = map head $ group $ sort [1..100]
| > $ ghci GroupKeyword.hs
| > GHCi, version 6.10.2: http://www.haskell.org/ghc/  :? for help
| > Loading package ghc-prim ... linking ... done.
| > Loading package integer ... linking ... done.
| > Loading package base ... linking ... done.
| > [1 of 1] Compiling GroupKeyword     ( GroupKeyword.hs, interpreted )
| >
| > GroupKeyword.hs:4:15: parse error on input `group'
| > Failed, modules loaded: none.
| > Prelude>
| 
| There are some places I'd like to use TransformListComp, but I often
| want to use group in the same module.
| 
| Thanks
| 
| Neil
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