2 % (c) The GRASP/AQUA Project, Glasgow University, 1992-1996
4 \section[MatchLit]{Pattern-matching literal patterns}
7 module MatchLit ( matchLiterals ) where
9 #include "HsVersions.h"
11 import {-# SOURCE #-} Match ( match )
12 import {-# SOURCE #-} DsExpr ( dsExpr )
14 import HsSyn ( HsLit(..), OutPat(..), HsExpr(..), Fixity,
15 Match, HsBinds, Stmt(..), DoOrListComp, HsType, ArithSeqInfo )
16 import TcHsSyn ( TypecheckedHsExpr, TypecheckedHsBinds,
19 import CoreSyn ( CoreExpr, CoreBinding, GenCoreExpr(..), GenCoreBinding(..) )
20 import Id ( GenId {- instance Eq -}, Id )
25 import Literal ( mkMachInt, Literal(..) )
26 import Maybes ( catMaybes )
27 import Type ( isUnpointedType, Type )
28 import Util ( panic, assertPanic )
37 This first one is a {\em special case} where the literal patterns are
38 unboxed numbers (NB: the fiddling introduced by @tidyEqnInfo@). We
39 want to avoid using the ``equality'' stuff provided by the
40 typechecker, and do a real ``case'' instead. In that sense, the code
41 is much like @matchConFamily@, which uses @match_cons_used@ to create
42 the alts---here we use @match_prims_used@.
45 matchLiterals all_vars@(var:vars) eqns_info@(EqnInfo n ctx (LitPat literal lit_ty : ps1) _ : eqns)
46 = -- GENERATE THE ALTS
47 match_prims_used vars eqns_info `thenDs` \ prim_alts ->
49 -- MAKE THE PRIMITIVE CASE
50 mkCoPrimCaseMatchResult var prim_alts
52 match_prims_used _ [{-no more eqns-}] = returnDs []
54 match_prims_used vars eqns_info@(EqnInfo n ctx ((LitPat literal lit_ty):ps1) _ : eqns)
56 (shifted_eqns_for_this_lit, eqns_not_for_this_lit)
57 = partitionEqnsByLit Nothing literal eqns_info
59 -- recursive call to make other alts...
60 match_prims_used vars eqns_not_for_this_lit `thenDs` \ rest_of_alts ->
62 -- (prim pats have no args; no selectMatchVars as in match_cons_used)
63 -- now do the business to make the alt for _this_ LitPat ...
64 match vars shifted_eqns_for_this_lit `thenDs` \ match_result ->
66 (mk_core_lit lit_ty literal, match_result)
70 mk_core_lit :: Type -> HsLit -> Literal
72 mk_core_lit ty (HsIntPrim i) = mkMachInt i
73 mk_core_lit ty (HsCharPrim c) = MachChar c
74 mk_core_lit ty (HsStringPrim s) = MachStr s
75 mk_core_lit ty (HsFloatPrim f) = MachFloat f
76 mk_core_lit ty (HsDoublePrim d) = MachDouble d
77 mk_core_lit ty (HsLitLit s) = ASSERT(isUnpointedType ty)
78 MachLitLit s (panic "MatchLit.matchLiterals:mk_core_lit:HsLitLit; typePrimRep???")
79 mk_core_lit ty other = panic "matchLiterals:mk_core_lit:unhandled"
83 matchLiterals all_vars@(var:vars) eqns_info@(EqnInfo n ctx ((NPat literal lit_ty eq_chk):ps1) _ : eqns)
85 (shifted_eqns_for_this_lit, eqns_not_for_this_lit)
86 = partitionEqnsByLit Nothing literal eqns_info
88 dsExpr (HsApp eq_chk (HsVar var)) `thenDs` \ pred_expr ->
89 match vars shifted_eqns_for_this_lit `thenDs` \ inner_match_result ->
90 mkGuardedMatchResult pred_expr inner_match_result `thenDs` \ match_result1 ->
92 if (null eqns_not_for_this_lit)
94 returnDs match_result1
96 matchLiterals all_vars eqns_not_for_this_lit `thenDs` \ match_result2 ->
97 combineMatchResults match_result1 match_result2
100 For an n+k pattern, we use the various magic expressions we've been given.
105 in <expr-for-a-successful-match>
107 <try-next-pattern-or-whatever>
112 matchLiterals all_vars@(var:vars) eqns_info@(EqnInfo n ctx ((NPlusKPat master_n k ty ge sub):ps1) _ : eqns)
114 (shifted_eqns_for_this_lit, eqns_not_for_this_lit)
115 = partitionEqnsByLit (Just master_n) k eqns_info
117 match vars shifted_eqns_for_this_lit `thenDs` \ inner_match_result ->
119 dsExpr (HsApp ge (HsVar var)) `thenDs` \ ge_expr ->
120 dsExpr (HsApp sub (HsVar var)) `thenDs` \ nminusk_expr ->
124 (mkCoLetsMatchResult [NonRec master_n nminusk_expr] inner_match_result)
125 `thenDs` \ match_result1 ->
127 if (null eqns_not_for_this_lit)
129 returnDs match_result1
131 matchLiterals all_vars eqns_not_for_this_lit `thenDs` \ match_result2 ->
132 combineMatchResults match_result1 match_result2
135 Given a blob of LitPats/NPats, we want to split them into those
136 that are ``same''/different as one we are looking at. We need to know
137 whether we're looking at a LitPat/NPat, and what literal we're after.
140 partitionEqnsByLit :: Maybe Id -- (Just v) for N-plus-K patterns, where v
141 -- is the "master" variable;
142 -- Nothing for NPats and LitPats
145 -> ([EquationInfo], -- These ones are for this lit, AND
146 -- they've been "shifted" by stripping
147 -- off the first pattern
148 [EquationInfo] -- These are not for this lit; they
149 -- are exactly as fed in.
152 partitionEqnsByLit nPlusK lit eqns
153 = ( \ (xs,ys) -> (catMaybes xs, catMaybes ys))
154 (unzip (map (partition_eqn nPlusK lit) eqns))
156 partition_eqn :: Maybe Id -> HsLit -> EquationInfo ->
157 (Maybe EquationInfo, Maybe EquationInfo)
159 partition_eqn Nothing lit (EqnInfo n ctx (LitPat k _ : remaining_pats) match_result)
160 | lit `eq_lit` k = (Just (EqnInfo n ctx remaining_pats match_result), Nothing)
161 -- NB the pattern is stripped off the EquationInfo
163 partition_eqn Nothing lit (EqnInfo n ctx (NPat k _ _ : remaining_pats) match_result)
164 | lit `eq_lit` k = (Just (EqnInfo n ctx remaining_pats match_result), Nothing)
165 -- NB the pattern is stripped off the EquationInfo
167 partition_eqn (Just master_n) lit (EqnInfo n ctx (NPlusKPat n' k _ _ _ : remaining_pats) match_result)
168 | lit `eq_lit` k = (Just (EqnInfo n ctx remaining_pats new_match_result), Nothing)
169 -- NB the pattern is stripped off the EquationInfo
171 new_match_result | master_n == n' = match_result
172 | otherwise = mkCoLetsMatchResult [NonRec n' (Var master_n)] match_result
174 -- Wild-card patterns, which will only show up in the shadows, go into both groups
175 partition_eqn nPlusK lit eqn@(EqnInfo n ctx (WildPat _ : remaining_pats) match_result)
176 = (Just (EqnInfo n ctx remaining_pats match_result), Just eqn)
178 -- Default case; not for this pattern
179 partition_eqn nPlusK lit eqn = (Nothing, Just eqn)
181 -- ToDo: meditate about this equality business...
183 eq_lit (HsInt i1) (HsInt i2) = i1 == i2
184 eq_lit (HsFrac f1) (HsFrac f2) = f1 == f2
186 eq_lit (HsIntPrim i1) (HsIntPrim i2) = i1 == i2
187 eq_lit (HsFloatPrim f1) (HsFloatPrim f2) = f1 == f2
188 eq_lit (HsDoublePrim d1) (HsDoublePrim d2) = d1 == d2
189 eq_lit (HsChar c1) (HsChar c2) = c1 == c2
190 eq_lit (HsCharPrim c1) (HsCharPrim c2) = c1 == c2
191 eq_lit (HsString s1) (HsString s2) = s1 == s2
192 eq_lit (HsStringPrim s1) (HsStringPrim s2) = s1 == s2
193 eq_lit (HsLitLit s1) (HsLitLit s2) = s1 == s2 -- ToDo: ??? (dubious)
194 eq_lit other1 other2 = panic "matchLiterals:eq_lit"