[project @ 1997-03-14 07:52:06 by simonpj]

[ghc-hetmet.git] / ghc / compiler / deSugar / MatchLit.lhs

diff --git a/ghc/compiler/deSugar/MatchLit.lhs b/ghc/compiler/deSugar/MatchLit.lhs
index a4ed52d..c7e4bc1 100644 (file)
--- a/ghc/compiler/deSugar/MatchLit.lhs
+++ b/ghc/compiler/deSugar/MatchLit.lhs
@@ -12,11 +12,12 @@ IMP_Ubiq()
 IMPORT_DELOOPER(DsLoop)                -- break match-ish and dsExpr-ish loops
 
 import HsSyn           ( HsLit(..), OutPat(..), HsExpr(..), Fixity,
-                         Match, HsBinds, Stmt, Qualifier, HsType, ArithSeqInfo )
+                         Match, HsBinds, Stmt(..), DoOrListComp, HsType, ArithSeqInfo )
 import TcHsSyn         ( SYN_IE(TypecheckedHsExpr), SYN_IE(TypecheckedHsBinds),
                          SYN_IE(TypecheckedPat)
                        )
-import CoreSyn         ( SYN_IE(CoreExpr), SYN_IE(CoreBinding) )
+import CoreSyn         ( SYN_IE(CoreExpr), SYN_IE(CoreBinding), GenCoreExpr(..), GenCoreBinding(..) )
+import Id              ( GenId {- instance Eq -} )
 
 import DsMonad
 import DsUtils
@@ -54,9 +55,9 @@ matchLiterals all_vars@(var:vars) eqns_info@(EqnInfo (LitPat literal lit_ty : ps
     match_prims_used vars eqns_info@(EqnInfo ((LitPat literal lit_ty):ps1) _ : eqns) shadows
       = let
            (shifted_eqns_for_this_lit, eqns_not_for_this_lit)
-             = partitionEqnsByLit literal eqns_info
+             = partitionEqnsByLit Nothing literal eqns_info
            (shifted_shadows_for_this_lit, shadows_not_for_this_lit)
-             = partitionEqnsByLit literal shadows
+             = partitionEqnsByLit Nothing literal shadows
        in
        -- recursive call to make other alts...
        match_prims_used vars eqns_not_for_this_lit shadows_not_for_this_lit    `thenDs` \ rest_of_alts ->
@@ -85,9 +86,9 @@ matchLiterals all_vars@(var:vars) eqns_info@(EqnInfo (LitPat literal lit_ty : ps
 matchLiterals all_vars@(var:vars) eqns_info@(EqnInfo ((NPat literal lit_ty eq_chk):ps1) _ : eqns) shadows
   = let
        (shifted_eqns_for_this_lit, eqns_not_for_this_lit)
-         = partitionEqnsByLit literal eqns_info
+         = partitionEqnsByLit Nothing literal eqns_info
        (shifted_shadows_for_this_lit, shadows_not_for_this_lit)
-         = partitionEqnsByLit literal shadows
+         = partitionEqnsByLit Nothing literal shadows
     in
     dsExpr (HsApp eq_chk (HsVar var))                                  `thenDs` \ pred_expr ->
     match vars shifted_eqns_for_this_lit shifted_shadows_for_this_lit  `thenDs` \ inner_match_result ->
@@ -111,12 +112,42 @@ We generate:
        <try-next-pattern-or-whatever>
 \end{verbatim}
 
+
+\begin{code}
+matchLiterals all_vars@(var:vars) eqns_info@(EqnInfo ((NPlusKPat master_n k ty ge sub):ps1) _ : eqns) shadows
+  = let
+       (shifted_eqns_for_this_lit, eqns_not_for_this_lit)
+         = partitionEqnsByLit (Just master_n) k eqns_info
+       (shifted_shadows_for_this_lit, shadows_not_for_this_lit)
+         = partitionEqnsByLit (Just master_n) k shadows
+    in
+    match vars shifted_eqns_for_this_lit shifted_shadows_for_this_lit  `thenDs` \ inner_match_result ->
+
+    dsExpr (HsApp ge (HsVar var))              `thenDs` \ ge_expr ->
+    dsExpr (HsApp sub (HsVar var))             `thenDs` \ nminusk_expr ->
+
+    mkGuardedMatchResult
+       ge_expr
+       (mkCoLetsMatchResult [NonRec master_n nminusk_expr] inner_match_result)
+                                       `thenDs` \ match_result1 ->
+
+    if (null eqns_not_for_this_lit)
+    then 
+       returnDs match_result1
+    else 
+       matchLiterals all_vars eqns_not_for_this_lit shadows_not_for_this_lit   `thenDs` \ match_result2 ->
+       combineMatchResults match_result1 match_result2
+\end{code}
+
 Given a blob of LitPats/NPats, we want to split them into those
 that are ``same''/different as one we are looking at.  We need to know
 whether we're looking at a LitPat/NPat, and what literal we're after.
 
 \begin{code}
-partitionEqnsByLit :: HsLit
+partitionEqnsByLit :: Maybe Id         -- (Just v) for N-plus-K patterns, where v
+                               -- is the "master" variable;
+                               -- Nothing for NPats and LitPats
+                  -> HsLit
                   -> [EquationInfo]
                   -> ([EquationInfo],  -- These ones are for this lit, AND
                                        -- they've been "shifted" by stripping
@@ -125,27 +156,34 @@ partitionEqnsByLit :: HsLit
                                        -- are exactly as fed in.
                      )
 
-partitionEqnsByLit lit eqns
+partitionEqnsByLit nPlusK lit eqns
   = ( \ (xs,ys) -> (catMaybes xs, catMaybes ys))
-       (unzip (map (partition_eqn lit) eqns))
+       (unzip (map (partition_eqn nPlusK lit) eqns))
   where
-    partition_eqn :: HsLit -> EquationInfo ->
+    partition_eqn :: Maybe Id -> HsLit -> EquationInfo ->
                (Maybe EquationInfo, Maybe EquationInfo)
 
-    partition_eqn lit (EqnInfo (LitPat k _ : remaining_pats) match_result)
+    partition_eqn Nothing lit (EqnInfo (LitPat k _ : remaining_pats) match_result)
       | lit `eq_lit` k  = (Just (EqnInfo remaining_pats match_result), Nothing)
-                         -- NB the pattern is stripped off thhe EquationInfo
+                         -- NB the pattern is stripped off the EquationInfo
 
-    partition_eqn lit (EqnInfo (NPat k _ _ : remaining_pats) match_result)
+    partition_eqn Nothing lit (EqnInfo (NPat k _ _ : remaining_pats) match_result)
       | lit `eq_lit` k  = (Just (EqnInfo remaining_pats match_result), Nothing)
-                         -- NB the pattern is stripped off thhe EquationInfo
+                         -- NB the pattern is stripped off the EquationInfo
+
+    partition_eqn (Just master_n) lit  (EqnInfo (NPlusKPat n k _ _ _ : remaining_pats) match_result)
+      | lit `eq_lit` k  = (Just (EqnInfo remaining_pats new_match_result), Nothing)
+                         -- NB the pattern is stripped off the EquationInfo
+      where
+       new_match_result | master_n == n = match_result
+                        | otherwise     = mkCoLetsMatchResult [NonRec n (Var master_n)] match_result
 
        -- Wild-card patterns, which will only show up in the shadows, go into both groups
-    partition_eqn lit eqn@(EqnInfo (WildPat _ : remaining_pats) match_result)
+    partition_eqn nPlusK lit eqn@(EqnInfo (WildPat _ : remaining_pats) match_result)
                        = (Just (EqnInfo remaining_pats match_result), Just eqn)
 
        -- Default case; not for this pattern
-    partition_eqn lit eqn = (Nothing, Just eqn)
+    partition_eqn nPlusK lit eqn = (Nothing, Just eqn)
 
 -- ToDo: meditate about this equality business...