[commit: ghc] master: Fix comments and documentation on monad comprehensions (e2ba862)

[Simon Peyton Jones]

Repository : ssh://darcs.haskell.org//srv/darcs/ghc

On branch  : master

http://hackage.haskell.org/trac/ghc/changeset/e2ba86228445cfe5faeedccb73a3ddea0a3b9026

>---------------------------------------------------------------

commit e2ba86228445cfe5faeedccb73a3ddea0a3b9026
Author: Simon Peyton Jones <simonpj at microsoft.com>
Date:   Wed Jul 27 06:22:26 2011 +0100

    Fix comments and documentation on monad comprehensions

>---------------------------------------------------------------

 compiler/hsSyn/HsExpr.lhs         |    8 ++++----
 docs/users_guide/glasgow_exts.xml |    6 ++++--
 2 files changed, 8 insertions(+), 6 deletions(-)

diff --git a/compiler/hsSyn/HsExpr.lhs b/compiler/hsSyn/HsExpr.lhs
index 4179423..1b556f3 100644
--- a/compiler/hsSyn/HsExpr.lhs
+++ b/compiler/hsSyn/HsExpr.lhs
@@ -944,10 +944,10 @@ data StmtLR idL idR
       }
   deriving (Data, Typeable)
 
-data TransForm		-- The 'f' below is the 'using' function, 'e' is the by function
-  = ThenForm		-- then f          or    then f by e
-  | GroupFormU		-- group using f   or    group using f by e
-  | GroupFormB    	-- group by e  
+data TransForm	 -- The 'f' below is the 'using' function, 'e' is the by function
+  = ThenForm	 -- then f          or    then f by e        (depending on trS_by)
+  | GroupFormU	 -- group using f   or    group using f by e (depending on trS_by)
+  | GroupFormB   -- group by e  
       -- In the GroupByFormB, trS_using is filled in with
       --    'groupWith' (list comprehensions) or 
       --    'groupM' (monad comprehensions)
diff --git a/docs/users_guide/glasgow_exts.xml b/docs/users_guide/glasgow_exts.xml
index 77d37c8..8aca42c 100644
--- a/docs/users_guide/glasgow_exts.xml
+++ b/docs/users_guide/glasgow_exts.xml
@@ -1382,13 +1382,15 @@ D[ e | (Q | R), S ]    = mzip D[ Qv | Q ] D[ Rv | R ] &gt;&gt;= \(Qv,Rv) -&gt; D
 -- Transform comprehensions
 D[ e | Q then f, R ]                  = f D[ Qv | Q ] &gt;&gt;= \Qv -&gt; D[ e | R ]
 
-D[ e | Q then f by b, R ]             = f b D[ Qv | Q ] &gt;&gt;= \Qv -&gt; D[ e | R ]
+D[ e | Q then f by b, R ]             = f (\Qv -&gt; b) D[ Qv | Q ] &gt;&gt;= \Qv -&gt; D[ e | R ]
 
 D[ e | Q then group using f, R ]      = f D[ Qv | Q ] &gt;&gt;= \ys -&gt;
                                         case (fmap selQv1 ys, ..., fmap selQvn ys) of
                                  	     Qv -&gt; D[ e | R ]
 
-D[ e | Q then group by b using f, R ] = f b D[ Qv | Q ] &gt;&gt;= \ys -&gt;
+D[ e | Q then group by b, R ]         = D[ e | Q then group by b using mgroupWith, R ]
+
+D[ e | Q then group by b using f, R ] = f (\Qv -&gt; b) D[ Qv | Q ] &gt;&gt;= \ys -&gt;
                                         case (fmap selQv1 ys, ..., fmap selQvn ys) of
                                            Qv -&gt; D[ e | R ]