\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"
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}
%************************************************************************
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)
%************************************************************************
%* *
- 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}
<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}
projects / ghc-hetmet.git / blobdiff