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