[project @ 1996-01-11 14:06:51 by partain]

[ghc-hetmet.git] / ghc / compiler / typecheck / TcMonad.lhs

diff --git a/ghc/compiler/typecheck/TcMonad.lhs b/ghc/compiler/typecheck/TcMonad.lhs
index 48cc7d9..dc947dc 100644 (file)
--- a/ghc/compiler/typecheck/TcMonad.lhs
+++ b/ghc/compiler/typecheck/TcMonad.lhs
@@ -14,7 +14,7 @@ module TcMonad (
        recoverTc, recoverQuietlyTc,
 
        NF_TcM(..),
-       thenNF_Tc, returnNF_Tc, listNF_Tc, mapNF_Tc,
+       thenNF_Tc, thenLazilyNF_Tc, returnNF_Tc, listNF_Tc, mapNF_Tc,
        fixNF_Tc, noFailTc,
 
        Baby_TcM(..), Baby_TcResult{-abstract-},
@@ -90,7 +90,7 @@ import SplitUniq
 import Unique
 import Util
 
-infixr 9 `thenTc`, `thenTc_`, `thenNF_Tc`
+infixr 9 `thenTc`, `thenTc_`, `thenNF_Tc`, `thenLazilyNF_Tc`
 \end{code}
 
 %************************************************************************
@@ -278,10 +278,12 @@ type NF_TcM result = InTcM (result, Subst, Bag Error)
 
 #ifdef __GLASGOW_HASKELL__
 {-# INLINE thenNF_Tc #-}
+{-# INLINE thenLazilyNF_Tc #-}
 {-# INLINE returnNF_Tc #-}
 #endif
 
-thenNF_Tc :: NF_TcM a -> (a -> InTcM b) -> InTcM b
+thenNF_Tc, thenLazilyNF_Tc :: NF_TcM a -> (a -> InTcM b) -> InTcM b
+-- ...Lazily... is purely a performance thing (WDP 95/09)
 \end{code}
 
 In particular, @thenNF_Tc@ has all of these types:
@@ -298,6 +300,15 @@ thenNF_Tc expr cont sw_chkr dtys subst us errs src_loc
        -> cont result sw_chkr dtys subst2 s2 errs2 src_loc
     }
 
+thenLazilyNF_Tc expr cont sw_chkr dtys subst us errs src_loc
+  = let
+       (s1, s2) = splitUniqSupply us
+    in
+    case (expr sw_chkr dtys subst s1 errs src_loc) of {
+     (result, subst2, errs2)
+       -> cont result sw_chkr dtys subst2 s2 errs2 src_loc
+    }
+
 returnNF_Tc :: a -> NF_TcM a
 returnNF_Tc result sw_chkr dtys subst us errs src_loc
   = (result, subst, errs)