diff options
Diffstat (limited to 'ghc/compiler/deSugar/MatchLit.lhs')
| -rw-r--r-- | ghc/compiler/deSugar/MatchLit.lhs | 294 |
1 files changed, 171 insertions, 123 deletions
diff --git a/ghc/compiler/deSugar/MatchLit.lhs b/ghc/compiler/deSugar/MatchLit.lhs index d3f04f46af..ea307ac45c 100644 --- a/ghc/compiler/deSugar/MatchLit.lhs +++ b/ghc/compiler/deSugar/MatchLit.lhs @@ -4,7 +4,8 @@ \section[MatchLit]{Pattern-matching literal patterns} \begin{code} -module MatchLit ( dsLit, matchLiterals ) where +module MatchLit ( dsLit, tidyLitPat, tidyNPat, + matchLiterals, matchNPlusKPats, matchNPats ) where #include "HsVersions.h" @@ -18,15 +19,18 @@ import HsSyn import Id ( Id ) import CoreSyn import TyCon ( tyConDataCons ) -import TcType ( tcSplitTyConApp, isIntegerTy ) +import TcType ( tcSplitTyConApp, isIntegerTy, isIntTy, isFloatTy, isDoubleTy ) +import Type ( Type ) import PrelNames ( ratioTyConKey ) +import TysWiredIn ( stringTy, consDataCon, intDataCon, floatDataCon, doubleDataCon ) import Unique ( hasKey ) import Literal ( mkMachInt, Literal(..) ) -import Maybes ( catMaybes ) -import SrcLoc ( noLoc, Located(..), unLoc ) -import Panic ( panic, assertPanic ) +import SrcLoc ( noLoc, unLoc ) +import ListSetOps ( equivClasses, runs ) import Ratio ( numerator, denominator ) +import SrcLoc ( Located(..) ) import Outputable +import FastString ( lengthFS, unpackFS ) \end{code} %************************************************************************ @@ -54,7 +58,7 @@ See also below where we look for @DictApps@ for \tr{plusInt}, etc. dsLit :: HsLit -> DsM CoreExpr dsLit (HsChar c) = returnDs (mkCharExpr c) dsLit (HsCharPrim c) = returnDs (mkLit (MachChar c)) -dsLit (HsString str) = mkStringLitFS str +dsLit (HsString str) = mkStringExprFS str dsLit (HsStringPrim s) = returnDs (mkLit (MachStr s)) dsLit (HsInteger i _) = mkIntegerExpr i dsLit (HsInt i) = returnDs (mkIntExpr i) @@ -75,79 +79,109 @@ dsLit (HsRat r ty) %************************************************************************ %* * - Pattern matching on literals + Tidying lit pats %* * %************************************************************************ \begin{code} -matchLiterals :: [Id] - -> [EquationInfo] - -> DsM MatchResult +tidyLitPat :: HsLit -> LPat Id -> LPat Id +-- Result has only the following HsLits: +-- HsIntPrim, HsCharPrim, HsFloatPrim +-- HsDoublePrim, HsStringPrim ? +-- * HsInteger, HsRat, HsInt can't show up in LitPats, +-- * HsString has been turned into an NPat in tcPat +-- and we get rid of HsChar right here +tidyLitPat (HsChar c) pat = mkCharLitPat c +tidyLitPat lit pat = pat + +tidyNPat :: HsLit -> Type -> LPat Id -> LPat Id +tidyNPat (HsString s) _ pat + | lengthFS s <= 1 -- Short string literals only + = foldr (\c pat -> mkPrefixConPat consDataCon [mkCharLitPat c,pat] stringTy) + (mkNilPat stringTy) (unpackFS s) + -- The stringTy is the type of the whole pattern, not + -- the type to instantiate (:) or [] with! + +tidyNPat lit lit_ty default_pat + | isIntTy lit_ty = mkPrefixConPat intDataCon [noLoc $ LitPat (mk_int lit)] lit_ty + | isFloatTy lit_ty = mkPrefixConPat floatDataCon [noLoc $ LitPat (mk_float lit)] lit_ty + | isDoubleTy lit_ty = mkPrefixConPat doubleDataCon [noLoc $ LitPat (mk_double lit)] lit_ty + | otherwise = default_pat + + where + mk_int (HsInteger i _) = HsIntPrim i + + mk_float (HsInteger i _) = HsFloatPrim (fromInteger i) + mk_float (HsRat f _) = HsFloatPrim f + + mk_double (HsInteger i _) = HsDoublePrim (fromInteger i) + mk_double (HsRat f _) = HsDoublePrim f \end{code} -This first one is a {\em special case} where the literal patterns are -unboxed numbers (NB: the fiddling introduced by @tidyEqnInfo@). We -want to avoid using the ``equality'' stuff provided by the -typechecker, and do a real ``case'' instead. In that sense, the code -is much like @matchConFamily@, which uses @match_cons_used@ to create -the alts---here we use @match_prims_used@. + +%************************************************************************ +%* * + Pattern matching on LitPat +%* * +%************************************************************************ \begin{code} -matchLiterals all_vars@(var:vars) eqns_info@(EqnInfo n ctx (LitPat literal : ps1) _ : eqns) - = -- GENERATE THE ALTS - match_prims_used vars eqns_info `thenDs` \ prim_alts -> +matchLiterals :: [Id] -> Type -> [EquationInfo] -> DsM MatchResult +-- All the EquationInfos have LitPats at the front + +matchLiterals (var:vars) ty eqns + = do { -- GROUP BY LITERAL + let groups :: [[(Literal, EquationInfo)]] + groups = equivClasses cmpTaggedEqn (tagLitEqns eqns) - -- MAKE THE PRIMITIVE CASE - returnDs (mkCoPrimCaseMatchResult var prim_alts) + -- DO THE MATCHING FOR EACH GROUP + ; alts <- mapM match_group groups + + -- MAKE THE PRIMITIVE CASE + ; return (mkCoPrimCaseMatchResult var ty alts) } where - match_prims_used _ [{-no more eqns-}] = returnDs [] - - match_prims_used vars eqns_info@(EqnInfo n ctx (pat@(LitPat literal):ps1) _ : eqns) - = let - (shifted_eqns_for_this_lit, eqns_not_for_this_lit) - = partitionEqnsByLit pat eqns_info - in - -- recursive call to make other alts... - match_prims_used vars eqns_not_for_this_lit `thenDs` \ rest_of_alts -> - - -- (prim pats have no args; no selectMatchVars as in match_cons_used) - -- now do the business to make the alt for _this_ LitPat ... - match vars shifted_eqns_for_this_lit `thenDs` \ match_result -> - returnDs ( - (mk_core_lit literal, match_result) - : rest_of_alts - ) - where - mk_core_lit :: HsLit -> Literal - - mk_core_lit (HsIntPrim i) = mkMachInt i - mk_core_lit (HsCharPrim c) = MachChar c - mk_core_lit (HsStringPrim s) = MachStr s - mk_core_lit (HsFloatPrim f) = MachFloat f - mk_core_lit (HsDoublePrim d) = MachDouble d - mk_core_lit other = panic "matchLiterals:mk_core_lit:unhandled" + match_group :: [(Literal, EquationInfo)] -> DsM (Literal, MatchResult) + match_group group + = do { let (lits, eqns) = unzip group + ; match_result <- match vars ty (shiftEqns eqns) + ; return (head lits, match_result) } \end{code} +%************************************************************************ +%* * + Pattern matching on NPat +%* * +%************************************************************************ + \begin{code} -matchLiterals all_vars@(var:vars) - eqns_info@(EqnInfo n ctx (pat@(NPatOut literal lit_ty eq_chk):ps1) _ : eqns) - = let - (shifted_eqns_for_this_lit, eqns_not_for_this_lit) - = partitionEqnsByLit pat eqns_info - in - dsExpr (HsApp (noLoc eq_chk) (nlHsVar var)) `thenDs` \ pred_expr -> - match vars shifted_eqns_for_this_lit `thenDs` \ inner_match_result -> - let - match_result1 = mkGuardedMatchResult pred_expr inner_match_result - in - if (null eqns_not_for_this_lit) - then - returnDs match_result1 - else - matchLiterals all_vars eqns_not_for_this_lit `thenDs` \ match_result2 -> - returnDs (combineMatchResults match_result1 match_result2) +matchNPats :: [Id] -> Type -> [EquationInfo] -> DsM MatchResult +-- All the EquationInfos have NPatOut at the front + +matchNPats (var:vars) ty eqns + = do { let groups :: [[(Literal, EquationInfo)]] + groups = equivClasses cmpTaggedEqn (tagLitEqns eqns) + + ; match_results <- mapM (match_group . map snd) groups + + ; ASSERT( not (null match_results) ) + return (foldr1 combineMatchResults match_results) } + where + match_group :: [EquationInfo] -> DsM MatchResult + match_group eqns + = do { pred_expr <- dsExpr (HsApp (noLoc eq_chk) (nlHsVar var)) + ; match_result <- match vars ty (shiftEqns eqns) + ; return (mkGuardedMatchResult pred_expr match_result) } + where + NPatOut _ _ eq_chk = firstPat (head eqns) \end{code} + +%************************************************************************ +%* * + Pattern matching on n+k patterns +%* * +%************************************************************************ + For an n+k pattern, we use the various magic expressions we've been given. We generate: \begin{verbatim} @@ -158,74 +192,88 @@ We generate: <try-next-pattern-or-whatever> \end{verbatim} +WATCH OUT! Consider + + f (n+1) = ... + f (n+2) = ... + f (n+1) = ... + +We can't group the first and third together, because the second may match +the same thing as the first. Contrast + f 1 = ... + f 2 = ... + f 1 = ... +where we can group the first and third. Hence 'runs' rather than 'equivClasses' \begin{code} -matchLiterals all_vars@(var:vars) eqns_info@(EqnInfo n ctx (pat@(NPlusKPatOut master_n k ge sub):ps1) _ : eqns) - = let - (shifted_eqns_for_this_lit, eqns_not_for_this_lit) - = partitionEqnsByLit pat eqns_info - in - match vars shifted_eqns_for_this_lit `thenDs` \ inner_match_result -> - - dsExpr (HsApp (noLoc ge) (nlHsVar var)) `thenDs` \ ge_expr -> - dsExpr (HsApp (noLoc sub) (nlHsVar var)) `thenDs` \ nminusk_expr -> - - let - match_result1 = mkGuardedMatchResult ge_expr $ - mkCoLetsMatchResult [NonRec (unLoc master_n) nminusk_expr] $ - inner_match_result - in - if (null eqns_not_for_this_lit) - then - returnDs match_result1 - else - matchLiterals all_vars eqns_not_for_this_lit `thenDs` \ match_result2 -> - returnDs (combineMatchResults match_result1 match_result2) +matchNPlusKPats all_vars@(var:vars) ty eqns + = do { let groups :: [[(Literal, EquationInfo)]] + groups = runs eqTaggedEqn (tagLitEqns eqns) + + ; match_results <- mapM (match_group . map snd) groups + + ; ASSERT( not (null match_results) ) + return (foldr1 combineMatchResults match_results) } + where + match_group :: [EquationInfo] -> DsM MatchResult + match_group eqns + = do { ge_expr <- dsExpr (HsApp (noLoc ge) (nlHsVar var)) + ; minusk_expr <- dsExpr (HsApp (noLoc sub) (nlHsVar var)) + ; match_result <- match vars ty (shiftEqns eqns) + ; return (mkGuardedMatchResult ge_expr $ + mkCoLetsMatchResult [NonRec n1 minusk_expr] $ + bindInMatchResult (map line_up other_pats) $ + match_result) } + where + (NPlusKPatOut (L _ n1) _ ge sub : other_pats) = map firstPat eqns + line_up (NPlusKPatOut (L _ n) _ _ _) = (n,n1) \end{code} + +%************************************************************************ +%* * + Grouping functions +%* * +%************************************************************************ + Given a blob of @LitPat@s/@NPat@s, 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 :: Pat Id - -> [EquationInfo] - -> ([EquationInfo], -- These ones are for this lit, AND - -- they've been "shifted" by stripping - -- off the first pattern - [EquationInfo] -- These are not for this lit; they - -- are exactly as fed in. - ) - -partitionEqnsByLit master_pat eqns - = ( \ (xs,ys) -> (catMaybes xs, catMaybes ys)) - (unzip (map (partition_eqn master_pat) eqns)) +-- Tag equations by the leading literal +-- NB: we have ordering on Core Literals, but not on HsLits +cmpTaggedEqn :: (Literal,EquationInfo) -> (Literal,EquationInfo) -> Ordering +cmpTaggedEqn (lit1,_) (lit2,_) = lit1 `compare` lit2 + +eqTaggedEqn :: (Literal,EquationInfo) -> (Literal,EquationInfo) -> Bool +eqTaggedEqn (lit1,_) (lit2,_) = lit1 == lit2 + +tagLitEqns :: [EquationInfo] -> [(Literal, EquationInfo)] +tagLitEqns eqns + = [(get_lit eqn, eqn) | eqn <- eqns] where - partition_eqn :: Pat Id -> EquationInfo -> (Maybe EquationInfo, Maybe EquationInfo) - - partition_eqn (LitPat k1) (EqnInfo n ctx (LitPat k2 : remaining_pats) match_result) - | k1 == k2 = (Just (EqnInfo n ctx remaining_pats match_result), Nothing) - -- NB the pattern is stripped off the EquationInfo - - partition_eqn (NPatOut k1 _ _) (EqnInfo n ctx (NPatOut k2 _ _ : remaining_pats) match_result) - | k1 == k2 = (Just (EqnInfo n ctx remaining_pats match_result), Nothing) - -- NB the pattern is stripped off the EquationInfo - - partition_eqn (NPlusKPatOut (L _ master_n) k1 _ _) - (EqnInfo n ctx (NPlusKPatOut (L _ n') k2 _ _ : remaining_pats) match_result) - | k1 == k2 = (Just (EqnInfo n ctx 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 master_pat eqn@(EqnInfo n ctx (WildPat _ : remaining_pats) match_result) - = (Just (EqnInfo n ctx remaining_pats match_result), Just eqn) - - -- Default case; not for this pattern - partition_eqn master_pat eqn = (Nothing, Just eqn) + get_lit eqn = case firstPat eqn of + LitPat hs_lit -> mk_core_lit hs_lit + NPatOut hs_lit _ _ -> mk_core_lit hs_lit + NPlusKPatOut _ i _ _ -> MachInt i + other -> panic "tagLitEqns:bad pattern" + +mk_core_lit :: HsLit -> Literal +mk_core_lit (HsIntPrim i) = mkMachInt i +mk_core_lit (HsCharPrim c) = MachChar c +mk_core_lit (HsStringPrim s) = MachStr s +mk_core_lit (HsFloatPrim f) = MachFloat f +mk_core_lit (HsDoublePrim d) = MachDouble d + + -- These ones are only needed in the NPatOut case, + -- and the Literal is only used as a key for grouping, + -- so the type doesn't matter. Actually I think HsInt, HsChar + -- can't happen, but it does no harm to include them +mk_core_lit (HsString s) = MachStr s +mk_core_lit (HsRat r _) = MachFloat r +mk_core_lit (HsInteger i _) = MachInt i +mk_core_lit (HsInt i) = MachInt i +mk_core_lit (HsChar c) = MachChar c \end{code} |