// Parse a single node, either an atom or a list in parens
// Handle macro expansion too
Node ParseNode()
{
// atom node
var sym = Take();
switch (sym.Atom)
{
case Atoms.IDENT:
return(IdentNode.Create(sym.Name, sym));
case Atoms.LITERAL:
return(LiteralNode.Create(sym.Value));
case Atoms.LP:
if (Check(Atoms.MACRO))
{
ExpandMacro(Take());
return(ParseNode());
}
else
{
var nodes = new List <Node>();
while (!Match(Atoms.RP))
{
nodes.Add(ParseNode());
}
return(ListNode.Create(nodes));
}
default:
throw ErrNotExpect(sym.Atom);
}
}
// check ident, return new node if undef or base scope
internal Node CheckedIdent(Node node)
{
if (node.IsIdent)
{
var ident = node as IdentNode;
if (!(ident.Sym.IsUndef || ident.Sym.IsBase))
{
throw Error.Assert("checked ident {0}", ident);
}
var newsym = _symbols.Find(ident.Sym.Name);
if (newsym != null && !newsym.IsUndef)
{
return(IdentNode.Create(ident.Name, newsym));
}
}
return(node);
}