[commit: ghc] imp-param-class: Add a function to deconstruct IP predicates. (82ee7cf)

[Iavor Diatchki]

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

On branch  : imp-param-class

http://hackage.haskell.org/trac/ghc/changeset/82ee7cfdf4bec20050fbf24b3119eeb085b01427

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

commit 82ee7cfdf4bec20050fbf24b3119eeb085b01427
Author: Iavor S. Diatchki <iavor.diatchki at gmail.com>
Date:   Sun Jun 10 16:55:57 2012 -0700

    Add a function to deconstruct IP predicates.

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

 compiler/types/Type.lhs |   10 +++++++++-
 1 files changed, 9 insertions(+), 1 deletions(-)

diff --git a/compiler/types/Type.lhs b/compiler/types/Type.lhs
index b977b25..1099303 100644
--- a/compiler/types/Type.lhs
+++ b/compiler/types/Type.lhs
@@ -53,7 +53,7 @@ module Type (
 	isDictLikeTy,
         mkEqPred, mkPrimEqPred,
         mkClassPred,
-        noParenPred, isClassPred, isEqPred, isIPPred,
+        noParenPred, isClassPred, isEqPred, isIPPred, isIPPred_maybe,
         
         -- Deconstructing predicate types
         PredTree(..), predTreePredType, classifyPredType,
@@ -165,6 +165,7 @@ import FastString
 import Data.List        ( partition )
 import Maybes		( orElse )
 import Data.Maybe	( isJust )
+import Control.Monad    ( guard )
 
 infixr 3 `mkFunTy`	-- Associates to the right
 \end{code}
@@ -857,6 +858,13 @@ isEqPred ty = case tyConAppTyCon_maybe ty of
 isIPPred ty = case tyConAppTyCon_maybe ty of
     Just tyCon -> tyConName tyCon == ipClassName
     _          -> False
+
+isIPPred_maybe :: Type -> Maybe (FastString, Type)
+isIPPred_maybe ty =
+  do (tc,[t1,t2]) <- splitTyConApp_maybe ty
+     guard (tyConName tc == ipClassName)
+     x <- isStrLitTy t1
+     return (x,t2)
 \end{code}
 
 Make PredTypes