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 #if defined(__GLASGOW_HASKELL__) && __GLASGOW_HASKELL__ <= 201
13 IMPORT_DELOOPER(DsLoop) -- break match-ish and dsExpr-ish loops
15 import {-# SOURCE #-} Match
16 import {-# SOURCE #-} DsExpr ( dsExpr )
19 import HsSyn ( HsLit(..), OutPat(..), HsExpr(..), Fixity,
20 Match, HsBinds, Stmt(..), DoOrListComp, HsType, ArithSeqInfo )
21 import TcHsSyn ( SYN_IE(TypecheckedHsExpr), SYN_IE(TypecheckedHsBinds),
22 SYN_IE(TypecheckedPat)
24 import CoreSyn ( SYN_IE(CoreExpr), SYN_IE(CoreBinding), GenCoreExpr(..), GenCoreBinding(..) )
25 import Id ( GenId {- instance Eq -}, SYN_IE(Id) )
30 import Literal ( mkMachInt, Literal(..) )
31 import Maybes ( catMaybes )
32 import Type ( isPrimType, SYN_IE(Type) )
33 import Util ( panic, assertPanic )
39 -> [EquationInfo] -- Shadows
43 This first one is a {\em special case} where the literal patterns are
44 unboxed numbers (NB: the fiddling introduced by @tidyEqnInfo@). We
45 want to avoid using the ``equality'' stuff provided by the
46 typechecker, and do a real ``case'' instead. In that sense, the code
47 is much like @matchConFamily@, which uses @match_cons_used@ to create
48 the alts---here we use @match_prims_used@.
51 matchLiterals all_vars@(var:vars) eqns_info@(EqnInfo (LitPat literal lit_ty : ps1) _ : eqns) shadows
52 = -- GENERATE THE ALTS
53 match_prims_used vars eqns_info shadows `thenDs` \ prim_alts ->
55 -- MAKE THE PRIMITIVE CASE
56 mkCoPrimCaseMatchResult var prim_alts
58 match_prims_used _ [{-no more eqns-}] _ = returnDs []
60 match_prims_used vars eqns_info@(EqnInfo ((LitPat literal lit_ty):ps1) _ : eqns) shadows
62 (shifted_eqns_for_this_lit, eqns_not_for_this_lit)
63 = partitionEqnsByLit Nothing literal eqns_info
64 (shifted_shadows_for_this_lit, shadows_not_for_this_lit)
65 = partitionEqnsByLit Nothing literal shadows
67 -- recursive call to make other alts...
68 match_prims_used vars eqns_not_for_this_lit shadows_not_for_this_lit `thenDs` \ rest_of_alts ->
70 -- (prim pats have no args; no selectMatchVars as in match_cons_used)
71 -- now do the business to make the alt for _this_ LitPat ...
72 match vars shifted_eqns_for_this_lit shifted_shadows_for_this_lit `thenDs` \ match_result ->
74 (mk_core_lit lit_ty literal, match_result)
78 mk_core_lit :: Type -> HsLit -> Literal
80 mk_core_lit ty (HsIntPrim i) = mkMachInt i
81 mk_core_lit ty (HsCharPrim c) = MachChar c
82 mk_core_lit ty (HsStringPrim s) = MachStr s
83 mk_core_lit ty (HsFloatPrim f) = MachFloat f
84 mk_core_lit ty (HsDoublePrim d) = MachDouble d
85 mk_core_lit ty (HsLitLit s) = ASSERT(isPrimType ty)
86 MachLitLit s (panic "MatchLit.matchLiterals:mk_core_lit:HsLitLit; typePrimRep???")
87 mk_core_lit ty other = panic "matchLiterals:mk_core_lit:unhandled"
91 matchLiterals all_vars@(var:vars) eqns_info@(EqnInfo ((NPat literal lit_ty eq_chk):ps1) _ : eqns) shadows
93 (shifted_eqns_for_this_lit, eqns_not_for_this_lit)
94 = partitionEqnsByLit Nothing literal eqns_info
95 (shifted_shadows_for_this_lit, shadows_not_for_this_lit)
96 = partitionEqnsByLit Nothing literal shadows
98 dsExpr (HsApp eq_chk (HsVar var)) `thenDs` \ pred_expr ->
99 match vars shifted_eqns_for_this_lit shifted_shadows_for_this_lit `thenDs` \ inner_match_result ->
100 mkGuardedMatchResult pred_expr inner_match_result `thenDs` \ match_result1 ->
102 if (null eqns_not_for_this_lit)
104 returnDs match_result1
106 matchLiterals all_vars eqns_not_for_this_lit shadows_not_for_this_lit `thenDs` \ match_result2 ->
107 combineMatchResults match_result1 match_result2
110 For an n+k pattern, we use the various magic expressions we've been given.
115 in <expr-for-a-successful-match>
117 <try-next-pattern-or-whatever>
122 matchLiterals all_vars@(var:vars) eqns_info@(EqnInfo ((NPlusKPat master_n k ty ge sub):ps1) _ : eqns) shadows
124 (shifted_eqns_for_this_lit, eqns_not_for_this_lit)
125 = partitionEqnsByLit (Just master_n) k eqns_info
126 (shifted_shadows_for_this_lit, shadows_not_for_this_lit)
127 = partitionEqnsByLit (Just master_n) k shadows
129 match vars shifted_eqns_for_this_lit shifted_shadows_for_this_lit `thenDs` \ inner_match_result ->
131 dsExpr (HsApp ge (HsVar var)) `thenDs` \ ge_expr ->
132 dsExpr (HsApp sub (HsVar var)) `thenDs` \ nminusk_expr ->
136 (mkCoLetsMatchResult [NonRec master_n nminusk_expr] inner_match_result)
137 `thenDs` \ match_result1 ->
139 if (null eqns_not_for_this_lit)
141 returnDs match_result1
143 matchLiterals all_vars eqns_not_for_this_lit shadows_not_for_this_lit `thenDs` \ match_result2 ->
144 combineMatchResults match_result1 match_result2
147 Given a blob of LitPats/NPats, we want to split them into those
148 that are ``same''/different as one we are looking at. We need to know
149 whether we're looking at a LitPat/NPat, and what literal we're after.
152 partitionEqnsByLit :: Maybe Id -- (Just v) for N-plus-K patterns, where v
153 -- is the "master" variable;
154 -- Nothing for NPats and LitPats
157 -> ([EquationInfo], -- These ones are for this lit, AND
158 -- they've been "shifted" by stripping
159 -- off the first pattern
160 [EquationInfo] -- These are not for this lit; they
161 -- are exactly as fed in.
164 partitionEqnsByLit nPlusK lit eqns
165 = ( \ (xs,ys) -> (catMaybes xs, catMaybes ys))
166 (unzip (map (partition_eqn nPlusK lit) eqns))
168 partition_eqn :: Maybe Id -> HsLit -> EquationInfo ->
169 (Maybe EquationInfo, Maybe EquationInfo)
171 partition_eqn Nothing lit (EqnInfo (LitPat k _ : remaining_pats) match_result)
172 | lit `eq_lit` k = (Just (EqnInfo remaining_pats match_result), Nothing)
173 -- NB the pattern is stripped off the EquationInfo
175 partition_eqn Nothing lit (EqnInfo (NPat k _ _ : remaining_pats) match_result)
176 | lit `eq_lit` k = (Just (EqnInfo remaining_pats match_result), Nothing)
177 -- NB the pattern is stripped off the EquationInfo
179 partition_eqn (Just master_n) lit (EqnInfo (NPlusKPat n k _ _ _ : remaining_pats) match_result)
180 | lit `eq_lit` k = (Just (EqnInfo remaining_pats new_match_result), Nothing)
181 -- NB the pattern is stripped off the EquationInfo
183 new_match_result | master_n == n = match_result
184 | otherwise = mkCoLetsMatchResult [NonRec n (Var master_n)] match_result
186 -- Wild-card patterns, which will only show up in the shadows, go into both groups
187 partition_eqn nPlusK lit eqn@(EqnInfo (WildPat _ : remaining_pats) match_result)
188 = (Just (EqnInfo remaining_pats match_result), Just eqn)
190 -- Default case; not for this pattern
191 partition_eqn nPlusK lit eqn = (Nothing, Just eqn)
193 -- ToDo: meditate about this equality business...
195 eq_lit (HsInt i1) (HsInt i2) = i1 == i2
196 eq_lit (HsFrac f1) (HsFrac f2) = f1 == f2
198 eq_lit (HsIntPrim i1) (HsIntPrim i2) = i1 == i2
199 eq_lit (HsFloatPrim f1) (HsFloatPrim f2) = f1 == f2
200 eq_lit (HsDoublePrim d1) (HsDoublePrim d2) = d1 == d2
201 eq_lit (HsChar c1) (HsChar c2) = c1 == c2
202 eq_lit (HsCharPrim c1) (HsCharPrim c2) = c1 == c2
203 eq_lit (HsString s1) (HsString s2) = s1 == s2
204 eq_lit (HsStringPrim s1) (HsStringPrim s2) = s1 == s2
205 eq_lit (HsLitLit s1) (HsLitLit s2) = s1 == s2 -- ToDo: ??? (dubious)
206 eq_lit other1 other2 = panic "matchLiterals:eq_lit"