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* Use a linked list of substitutions. This reduces the amount of

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copying.
This commit is contained in:
Eelco Dolstra 2006-05-02 21:39:02 +00:00
parent c791e94aee
commit 68174bdc7d
4 changed files with 54 additions and 19 deletions
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34
src/libexpr/nixexpr.cc
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@ -222,7 +222,7 @@ Expr makeAttrs(const ATermMap & attrs)
}
Expr substitute(const ATermMap & subs, Expr e)
Expr substitute(const Substitution & subs, Expr e)
{
checkInterrupt();
@ -235,7 +235,8 @@ Expr substitute(const ATermMap & subs, Expr e)
if (matchClosed(e, e2)) return e;
if (matchVar(e, name)) {
Expr sub = subs.get(name);
Expr sub = subs.lookup(name);
if (sub == makeRemoved()) sub = 0;
Expr wrapped;
/* Add a "closed" wrapper around terms that aren't already
closed. The check is necessary to prevent repeated
@ -249,36 +250,37 @@ Expr substitute(const ATermMap & subs, Expr e)
ATermList formals;
ATerm body, def;
if (matchFunction(e, formals, body, pos)) {
ATermMap subs2(subs);
ATermMap map;
for (ATermIterator i(formals); i; ++i) {
if (!matchNoDefFormal(*i, name) &&
!matchDefFormal(*i, name, def))
abort();
subs2.remove(name);
map.set(name, makeRemoved());
}
Substitution subs2(&subs, &map);
return makeFunction(
(ATermList) substitute(subs2, (ATerm) formals),
substitute(subs2, body), pos);
}
if (matchFunction1(e, name, body, pos)) {
ATermMap subs2(subs);
subs2.remove(name);
return makeFunction1(name, substitute(subs2, body), pos);
ATermMap map;
map.set(name, makeRemoved());
return makeFunction1(name, substitute(Substitution(&subs, &map), body), pos);
}
/* Idem for a mutually recursive attribute set. */
ATermList rbnds, nrbnds;
if (matchRec(e, rbnds, nrbnds)) {
ATermMap subs2(subs);
ATermMap map;
for (ATermIterator i(rbnds); i; ++i)
if (matchBind(*i, name, e2, pos)) subs2.remove(name);
if (matchBind(*i, name, e2, pos)) map.set(name, makeRemoved());
else abort(); /* can't happen */
for (ATermIterator i(nrbnds); i; ++i)
if (matchBind(*i, name, e2, pos)) subs2.remove(name);
if (matchBind(*i, name, e2, pos)) map.set(name, makeRemoved());
else abort(); /* can't happen */
return makeRec(
(ATermList) substitute(subs2, (ATerm) rbnds),
(ATermList) substitute(Substitution(&subs, &map), (ATerm) rbnds),
(ATermList) substitute(subs, (ATerm) nrbnds));
}
@ -286,11 +288,15 @@ Expr substitute(const ATermMap & subs, Expr e)
AFun fun = ATgetAFun(e);
int arity = ATgetArity(fun);
ATerm args[arity];
bool changed = false;
for (int i = 0; i < arity; ++i)
args[i] = substitute(subs, ATgetArgument(e, i));
for (int i = 0; i < arity; ++i) {
ATerm arg = ATgetArgument(e, i);
args[i] = substitute(subs, arg);
if (args[i] != arg) changed = true;
}
return (ATerm) ATmakeApplArray(fun, args);
return changed ? (ATerm) ATmakeApplArray(fun, args) : e;
}
if (ATgetType(e) == AT_LIST) {