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/* --------------------------------------------------------------------------
* Substitute variables in an expression
*
* The Hugs 98 system is Copyright (c) Mark P Jones, Alastair Reid, the
* Yale Haskell Group, and the Oregon Graduate Institute of Science and
* Technology, 1994-1999, All rights reserved. It is distributed as
* free software under the license in the file "License", which is
* included in the distribution.
*
* $RCSfile: stgSubst.c,v $
* $Revision: 1.7 $
* $Date: 2000/03/10 20:03:36 $
* ------------------------------------------------------------------------*/
#include "prelude.h"
#include "storage.h"
#include "connect.h"
#include "errors.h"
/* --------------------------------------------------------------------------
* Local function prototypes:
* ------------------------------------------------------------------------*/
static StgVar substVar ( List sub, StgVar v );
static StgAtom substAtom ( List sub, StgAtom a );
static void substBind ( List sub, StgVar bind );
static void substAlt ( List sub, StgCaseAlt alt );
static void substPrimAlt ( List sub, StgPrimAlt alt );
/* --------------------------------------------------------------------------
* Substitute variables throughout an expression - updating in place.
* ------------------------------------------------------------------------*/
static StgVar substVar( List sub, StgVar v )
{
Pair p = cellAssoc(v,sub);
if (nonNull(p)) {
return snd(p);
} else {
return v;
}
}
static StgAtom substAtom ( List sub, StgAtom a )
{
switch (whatIs(a)) {
case STGVAR:
return substVar(sub,a);
default:
return a;
}
}
static Void substBind( List sub, StgVar bind )
{
StgRhs rhs = stgVarBody(bind);
switch (whatIs(rhs)) {
case STGCON:
map1Over(substAtom,sub,stgConArgs(rhs));
return;
default:
stgVarBody(bind) = substExpr(sub,rhs);
return;
}
}
static Void substAlt( List sub, StgCaseAlt alt )
{
if (isDefaultAlt(alt))
stgDefaultBody(alt) = substExpr(sub,stgDefaultBody(alt)); else
stgCaseAltBody(alt) = substExpr(sub,stgCaseAltBody(alt));
}
static Void substPrimAlt( List sub, StgPrimAlt alt )
{
stgPrimAltBody(alt) = substExpr(sub,stgPrimAltBody(alt));
}
StgExpr substExpr( List sub, StgExpr e )
{
switch (whatIs(e)) {
case LETREC:
map1Proc(substBind,sub,stgLetBinds(e));
stgLetBody(e) = substExpr(sub,stgLetBody(e));
break;
case LAMBDA:
stgLambdaBody(e) = substExpr(sub,stgLambdaBody(e));
break;
case CASE:
stgCaseScrut(e) = substExpr(sub,stgCaseScrut(e));
map1Proc(substAlt,sub,stgCaseAlts(e));
break;
case PRIMCASE:
stgPrimCaseScrut(e) = substExpr(sub,stgPrimCaseScrut(e));
map1Proc(substPrimAlt,sub,stgPrimCaseAlts(e));
break;
case STGPRIM:
map1Over(substAtom,sub,stgPrimArgs(e));
break;
case STGAPP:
stgAppFun(e) = substVar(sub,stgAppFun(e));
map1Over(substAtom,sub,stgAppArgs(e));
break;
case STGCON:
map1Over(substAtom,sub,stgConArgs(e));
break;
case STGVAR:
case NAME:
return substVar(sub,e);
default:
internal("substExpr");
}
return e;
}
/*-------------------------------------------------------------------------*/
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