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* Allow function argument default values to refer to other arguments

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of the function.  Implements NIX-45.
This commit is contained in:
Eelco Dolstra 2006-05-08 12:52:47 +00:00
parent 310e605995
commit 5cabd47394
5 changed files with 51 additions and 39 deletions
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77
src/libexpr/eval.cc
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@ -24,49 +24,54 @@ void EvalState::addPrimOp(const string & name,
/* Substitute an argument set into the body of a function. */
static Expr substArgs(Expr body, ATermList formals, Expr arg)
{
ATermMap subs(ATgetLength(formals) * 2);
unsigned int nrFormals = ATgetLength(formals);
ATermMap subs(nrFormals);
/* ({x ? E1; y ? E2, z}: E3) {x = E4; z = E5;}
=> let {x = E4; y = E2; z = E5; body = E3; }
=> subst(E3, s)
s = {
R = rec {x = E4; y = E2; z = E5}
x -> R.x
y -> R.y
z -> R.z
}
*/
/* Get the formal arguments. */
for (ATermIterator i(formals); i; ++i) {
Expr name, def;
if (matchNoDefFormal(*i, name))
subs.set(name, makeUndefined());
else if (matchDefFormal(*i, name, def))
subs.set(name, def);
else abort(); /* can't happen */
}
/* Get the actual arguments, and check that they match with the
formals. */
/* Get the actual arguments and put them in the substitution. */
ATermMap args(128); /* !!! fix */
queryAllAttrs(arg, args);
for (ATermMap::const_iterator i = args.begin(); i != args.end(); ++i) {
Expr cur = subs.get(i->key);
if (!subs.get(i->key))
throw Error(format("unexpected function argument `%1%'")
% aterm2String(i->key));
for (ATermMap::const_iterator i = args.begin(); i != args.end(); ++i)
subs.set(i->key, i->value);
/* Get the formal arguments. */
ATermVector defsUsed;
ATermList recAttrs = ATempty;
for (ATermIterator i(formals); i; ++i) {
Expr name, def = 0;
if (!matchNoDefFormal(*i, name) && !matchDefFormal(*i, name, def))
abort(); /* can't happen */
if (subs[name] == 0) {
if (def == 0) throw Error(format("required function argument `%1%' missing")
% aterm2String(name));
defsUsed.push_back(name);
recAttrs = ATinsert(recAttrs, makeBind(name, def, makeNoPos()));
}
}
/* Check that all arguments are defined. */
for (ATermMap::const_iterator i = subs.begin(); i != subs.end(); ++i)
if (i->value == makeUndefined())
throw Error(format("required function argument `%1%' missing")
% aterm2String(i->key));
/* Make a recursive attribute set out of the (argument-name,
value) tuples. This is so that we can support default
parameters that refer to each other, e.g. ({x, y ? x + x}: y)
{x = "foo";} evaluates to "foofoo". */
if (defsUsed.size() != 0) {
for (ATermMap::const_iterator i = args.begin(); i != args.end(); ++i)
recAttrs = ATinsert(recAttrs, makeBind(i->key, i->value, makeNoPos()));
Expr rec = makeRec(recAttrs, ATempty);
for (ATermVector::iterator i = defsUsed.begin(); i != defsUsed.end(); ++i)
subs.set(*i, makeSelect(rec, *i));
}
if (subs.size() != nrFormals) {
/* One or more actual arguments were not declared as formal
arguments. Find out which. */
for (ATermIterator i(formals); i; ++i) {
Expr name, def;
matchNoDefFormal(*i, name) || matchDefFormal(*i, name, def);
subs.remove(name);
}
throw Error(format("unexpected function argument `%1%'")
% aterm2String(subs.begin()->key));
}
return substitute(Substitution(0, &subs), body);
}