%
-% (c) The GRASP/AQUA Project, Glasgow University, 1992-1995
+% (c) The GRASP/AQUA Project, Glasgow University, 1992-1996
%
\section[MatchCon]{Pattern-matching constructors}
\begin{code}
#include "HsVersions.h"
-module MatchCon (
- matchConFamily
-) where
-
-import AbsSyn -- the stuff being desugared
-import PlainCore -- the output of desugaring;
- -- importing this module also gets all the
- -- CoreSyn utility functions
-import DsMonad -- the monadery used in the desugarer
-
-import AbsUniType ( mkTyVarTy, splitType, TyVar, TyVarTemplate,
- getTyConDataCons,
- instantiateTauTy, TyCon, Class, UniType,
- TauType(..), InstTyEnv(..)
- IF_ATTACK_PRAGMAS(COMMA instantiateTy)
- )
+module MatchCon ( matchConFamily ) where
+
+import Ubiq
+import DsLoop ( match ) -- break match-ish loop
+
+import HsSyn ( OutPat(..), HsLit, HsExpr )
+import DsHsSyn ( outPatType )
+
+import DsMonad
import DsUtils
-import Id ( eqId, getInstantiatedDataConSig,
- getIdUniType, isDataCon, DataCon(..)
- )
-import Maybes ( Maybe(..) )
-import Match ( match )
-import Util
-\end{code}
-\subsection[matchConFamily]{Making alternatives for a constructor family}
+import Id ( isDataCon, GenId{-instances-} )
+import Util ( panic, assertPanic )
+\end{code}
We are confronted with the first column of patterns in a set of
equations, all beginning with constructors from one ``family'' (e.g.,
@[]@ and @:@ make up the @List@ ``family''). We want to generate the
-alternatives for a @CoCase@ expression. There are several choices:
+alternatives for a @Case@ expression. There are several choices:
\begin{enumerate}
\item
Generate an alternative for every constructor in the family, whether
chapter does.
\begin{description}
\item[Advantages:]
-(a)~Simple. (b)~It may also be that large sparsely-used constructor families are mainly
-handled by the code for literals.
+(a)~Simple. (b)~It may also be that large sparsely-used constructor
+families are mainly handled by the code for literals.
\item[Disadvantages:]
-(a)~Not practical for large sparsely-used constructor families, e.g., the
-ASCII character set. (b)~Have to look up (in the TDE environment) a
-list of what constructors make up the whole family. So far, this is
-the only part of desugaring that needs information from the environments.
+(a)~Not practical for large sparsely-used constructor families, e.g.,
+the ASCII character set. (b)~Have to look up a list of what
+constructors make up the whole family.
\end{description}
\item
\end{description}
\end{enumerate}
-We are implementing the ``do-it-right'' option for now.
-The arguments to @matchConFamily@ are the same as to @match@; the extra
-@Int@ returned is the number of constructors in the family.
+We are implementing the ``do-it-right'' option for now. The arguments
+to @matchConFamily@ are the same as to @match@; the extra @Int@
+returned is the number of constructors in the family.
The function @matchConFamily@ is concerned with this
-have-we-used-all-the-constructors question; the local function
+have-we-used-all-the-constructors? question; the local function
@match_cons_used@ does all the real work.
\begin{code}
matchConFamily :: [Id]
mkCoAlgCaseMatchResult var alts
\end{code}
-And here is the local function that does all the work. It is more-or-less the
-@matchCon@/@matchClause@ functions on page~94 in Wadler's chapter in SLPJ.
+And here is the local function that does all the work. It is
+more-or-less the @matchCon@/@matchClause@ functions on page~94 in
+Wadler's chapter in SLPJ.
\begin{code}
match_cons_used _ [{- no more eqns -}] _ = returnDs []
selectMatchVars arg_pats `thenDs` \ new_vars ->
-- Now do the business to make the alt for _this_ ConPat ...
- match (new_vars++vars)
- (map shift_con_pat eqns_for_this_con)
+ match (new_vars++vars)
+ (map shift_con_pat eqns_for_this_con)
(map shift_con_pat shadows_for_this_con) `thenDs` \ match_result ->
returnDs (
where
splitByCon :: [EquationInfo] -> ([EquationInfo], [EquationInfo])
splitByCon [] = ([],[])
- splitByCon (info@(EqnInfo (pat : _) _) : rest)
+ splitByCon (info@(EqnInfo (pat : _) _) : rest)
= case pat of
- ConPat n _ _ | n `eqId` data_con -> (info:rest_yes, rest_no)
- WildPat _ -> (info:rest_yes, info:rest_no)
- -- WildPats will be in the shadows only,
+ ConPat n _ _ | n == data_con -> (info:rest_yes, rest_no)
+ WildPat _ -> (info:rest_yes, info:rest_no)
+ -- WildPats will be in the shadows only,
-- and they go into both groups
- other_pat -> (rest_yes, info:rest_no)
+ other_pat -> (rest_yes, info:rest_no)
where
(rest_yes, rest_no) = splitByCon rest
shift_con_pat (EqnInfo (ConPat _ _ pats': pats) match_result)
= EqnInfo (pats' ++ pats) match_result
shift_con_pat (EqnInfo (WildPat _: pats) match_result) -- Will only happen in shadow
- = EqnInfo ([WildPat (typeOfPat arg_pat) | arg_pat <- arg_pats] ++ pats) match_result
+ = EqnInfo ([WildPat (outPatType arg_pat) | arg_pat <- arg_pats] ++ pats) match_result
shift_con_pat other = panic "matchConFamily:match_cons_used:shift_con_pat"
\end{code}
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