%
-% (c) The GRASP/AQUA Project, Glasgow University, 1992-1996
+% (c) The GRASP/AQUA Project, Glasgow University, 1992-1998
%
\section[MatchLit]{Pattern-matching literal patterns}
\begin{code}
-module MatchLit ( matchLiterals ) where
+module MatchLit ( dsLit, tidyLitPat, tidyNPat,
+ matchLiterals, matchNPlusKPats, matchNPats ) where
#include "HsVersions.h"
import {-# SOURCE #-} Match ( match )
import {-# SOURCE #-} DsExpr ( dsExpr )
-import HsSyn ( HsLit(..), OutPat(..), HsExpr(..), Fixity,
- Match, HsBinds, Stmt(..), DoOrListComp, HsType, ArithSeqInfo )
-import TcHsSyn ( TypecheckedHsExpr, TypecheckedHsBinds,
- TypecheckedPat
- )
-import CoreSyn ( CoreExpr, CoreBinding, GenCoreExpr(..), GenCoreBinding(..) )
-import Id ( GenId {- instance Eq -}, Id )
-
import DsMonad
import DsUtils
+import HsSyn
+import Id ( Id )
+import CoreSyn
+import TyCon ( tyConDataCons )
+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 Type ( isUnpointedType, Type )
-import Util ( panic, assertPanic )
+import SrcLoc ( noLoc )
+import ListSetOps ( equivClasses, runs )
+import Ratio ( numerator, denominator )
+import SrcLoc ( Located(..) )
+import Outputable
+import FastString ( lengthFS, unpackFS )
\end{code}
+%************************************************************************
+%* *
+ Desugaring literals
+ [used to be in DsExpr, but DsMeta needs it,
+ and it's nice to avoid a loop]
+%* *
+%************************************************************************
+
+We give int/float literals type @Integer@ and @Rational@, respectively.
+The typechecker will (presumably) have put \tr{from{Integer,Rational}s}
+around them.
+
+ToDo: put in range checks for when converting ``@i@''
+(or should that be in the typechecker?)
+
+For numeric literals, we try to detect there use at a standard type
+(@Int@, @Float@, etc.) are directly put in the right constructor.
+[NB: down with the @App@ conversion.]
+
+See also below where we look for @DictApps@ for \tr{plusInt}, etc.
+
\begin{code}
-matchLiterals :: [Id]
- -> [EquationInfo]
- -> DsM MatchResult
+dsLit :: HsLit -> DsM CoreExpr
+dsLit (HsChar c) = returnDs (mkCharExpr c)
+dsLit (HsCharPrim c) = returnDs (mkLit (MachChar c))
+dsLit (HsString str) = mkStringExprFS str
+dsLit (HsStringPrim s) = returnDs (mkLit (MachStr s))
+dsLit (HsInteger i _) = mkIntegerExpr i
+dsLit (HsInt i) = returnDs (mkIntExpr i)
+dsLit (HsIntPrim i) = returnDs (mkIntLit i)
+dsLit (HsFloatPrim f) = returnDs (mkLit (MachFloat f))
+dsLit (HsDoublePrim d) = returnDs (mkLit (MachDouble d))
+
+dsLit (HsRat r ty)
+ = mkIntegerExpr (numerator r) `thenDs` \ num ->
+ mkIntegerExpr (denominator r) `thenDs` \ denom ->
+ returnDs (mkConApp ratio_data_con [Type integer_ty, num, denom])
+ where
+ (ratio_data_con, integer_ty)
+ = case tcSplitTyConApp ty of
+ (tycon, [i_ty]) -> ASSERT(isIntegerTy i_ty && tycon `hasKey` ratioTyConKey)
+ (head (tyConDataCons tycon), i_ty)
\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@.
+%************************************************************************
+%* *
+ Tidying lit pats
+%* *
+%************************************************************************
\begin{code}
-matchLiterals all_vars@(var:vars) eqns_info@(EqnInfo n ctx (LitPat literal lit_ty : ps1) _ : eqns)
- = -- GENERATE THE ALTS
- match_prims_used vars eqns_info `thenDs` \ prim_alts ->
+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
- -- MAKE THE PRIMITIVE CASE
- mkCoPrimCaseMatchResult var prim_alts
where
- match_prims_used _ [{-no more eqns-}] = returnDs []
-
- match_prims_used vars eqns_info@(EqnInfo n ctx ((LitPat literal lit_ty):ps1) _ : eqns)
- = let
- (shifted_eqns_for_this_lit, eqns_not_for_this_lit)
- = partitionEqnsByLit Nothing literal 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 lit_ty literal, match_result)
- : rest_of_alts
- )
- where
- mk_core_lit :: Type -> HsLit -> Literal
-
- mk_core_lit ty (HsIntPrim i) = mkMachInt i
- mk_core_lit ty (HsCharPrim c) = MachChar c
- mk_core_lit ty (HsStringPrim s) = MachStr s
- mk_core_lit ty (HsFloatPrim f) = MachFloat f
- mk_core_lit ty (HsDoublePrim d) = MachDouble d
- mk_core_lit ty (HsLitLit s) = ASSERT(isUnpointedType ty)
- MachLitLit s (panic "MatchLit.matchLiterals:mk_core_lit:HsLitLit; typePrimRep???")
- mk_core_lit ty other = panic "matchLiterals:mk_core_lit:unhandled"
+ 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}
+
+%************************************************************************
+%* *
+ Pattern matching on LitPat
+%* *
+%************************************************************************
+
\begin{code}
-matchLiterals all_vars@(var:vars) eqns_info@(EqnInfo n ctx ((NPat literal lit_ty eq_chk):ps1) _ : eqns)
- = let
- (shifted_eqns_for_this_lit, eqns_not_for_this_lit)
- = partitionEqnsByLit Nothing literal eqns_info
- in
- dsExpr (HsApp eq_chk (HsVar var)) `thenDs` \ pred_expr ->
- match vars shifted_eqns_for_this_lit `thenDs` \ inner_match_result ->
- mkGuardedMatchResult pred_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 `thenDs` \ match_result2 ->
- combineMatchResults match_result1 match_result2
+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)
+
+ -- DO THE MATCHING FOR EACH GROUP
+ ; alts <- mapM match_group groups
+
+ -- MAKE THE PRIMITIVE CASE
+ ; return (mkCoPrimCaseMatchResult var ty alts) }
+ where
+ 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}
+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 (eqn1:eqns)
+ = do { pred_expr <- dsExpr (HsApp (noLoc eq_chk) (nlHsVar var))
+ ; match_result <- match vars ty (eqn1' : shiftEqns eqns)
+ ; return (adjustMatchResult (eqn_wrap eqn1) $
+ -- Bring the eqn1 wrapper stuff into scope because
+ -- it may be used in pred_expr
+ mkGuardedMatchResult pred_expr match_result) }
+ where
+ NPatOut _ _ eq_chk : pats1 = eqn_pats eqn1
+ eqn1' = eqn1 { eqn_wrap = idWrapper, eqn_pats = pats1 }
\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 ((NPlusKPat master_n k ty ge sub):ps1) _ : eqns)
- = let
- (shifted_eqns_for_this_lit, eqns_not_for_this_lit)
- = partitionEqnsByLit (Just master_n) k eqns_info
- in
- match vars shifted_eqns_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 `thenDs` \ match_result2 ->
- 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 (eqn1:eqns)
+ = do { ge_expr <- dsExpr (HsApp (noLoc ge) (nlHsVar var))
+ ; minusk_expr <- dsExpr (HsApp (noLoc sub) (nlHsVar var))
+ ; match_result <- match vars ty (eqn1' : map shift eqns)
+ ; return (adjustMatchResult (eqn_wrap eqn1) $
+ -- Bring the eqn1 wrapper stuff into scope because
+ -- it may be used in ge_expr, minusk_expr
+ mkGuardedMatchResult ge_expr $
+ mkCoLetMatchResult (NonRec n1 minusk_expr) $
+ match_result) }
+ where
+ NPlusKPatOut (L _ n1) _ ge sub : pats1 = eqn_pats eqn1
+ eqn1' = eqn1 { eqn_wrap = idWrapper, eqn_pats = pats1 }
+
+ shift eqn@(EqnInfo { eqn_wrap = wrap,
+ eqn_pats = NPlusKPatOut (L _ n) _ _ _ : pats })
+ = eqn { eqn_wrap = wrap . wrapBind n n1, eqn_pats = pats }
\end{code}
-Given a blob of LitPats/NPats, we want to split them into those
+
+%************************************************************************
+%* *
+ 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.
+whether we're looking at a @LitPat@/@NPat@, and what literal we're after.
\begin{code}
-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
- -- off the first pattern
- [EquationInfo] -- These are not for this lit; they
- -- are exactly as fed in.
- )
-
-partitionEqnsByLit nPlusK lit eqns
- = ( \ (xs,ys) -> (catMaybes xs, catMaybes ys))
- (unzip (map (partition_eqn nPlusK lit) 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 :: Maybe Id -> HsLit -> EquationInfo ->
- (Maybe EquationInfo, Maybe EquationInfo)
-
- partition_eqn Nothing lit (EqnInfo n ctx (LitPat k _ : remaining_pats) match_result)
- | lit `eq_lit` k = (Just (EqnInfo n ctx remaining_pats match_result), Nothing)
- -- NB the pattern is stripped off the EquationInfo
-
- partition_eqn Nothing lit (EqnInfo n ctx (NPat k _ _ : remaining_pats) match_result)
- | lit `eq_lit` k = (Just (EqnInfo n ctx remaining_pats match_result), Nothing)
- -- NB the pattern is stripped off the EquationInfo
-
- partition_eqn (Just master_n) lit (EqnInfo n ctx (NPlusKPat n' k _ _ _ : remaining_pats) match_result)
- | lit `eq_lit` k = (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 nPlusK lit 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 nPlusK lit eqn = (Nothing, Just eqn)
-
--- ToDo: meditate about this equality business...
-
-eq_lit (HsInt i1) (HsInt i2) = i1 == i2
-eq_lit (HsFrac f1) (HsFrac f2) = f1 == f2
-
-eq_lit (HsIntPrim i1) (HsIntPrim i2) = i1 == i2
-eq_lit (HsFloatPrim f1) (HsFloatPrim f2) = f1 == f2
-eq_lit (HsDoublePrim d1) (HsDoublePrim d2) = d1 == d2
-eq_lit (HsChar c1) (HsChar c2) = c1 == c2
-eq_lit (HsCharPrim c1) (HsCharPrim c2) = c1 == c2
-eq_lit (HsString s1) (HsString s2) = s1 == s2
-eq_lit (HsStringPrim s1) (HsStringPrim s2) = s1 == s2
-eq_lit (HsLitLit s1) (HsLitLit s2) = s1 == s2 -- ToDo: ??? (dubious)
-eq_lit other1 other2 = panic "matchLiterals:eq_lit"
+ 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}
+
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