Value Parse()
{
Value v = ParseFactor();
Gobble('LF');
Expect('EOF');
return v;
}
Value Parse()
{
Value v = ParseFactor();
Gobble(T_LINEFEED);
Expect(T_ENDOFFILE);
return v;
}
Value ParseFactor()
{
switch (lex.token)
{
case 'INT': { int i = atoi(lex.sattr.c_str()); lex.Next(); return Value(i); }
case 'FLT': { double f = atof(lex.sattr.c_str()); lex.Next(); return Value((float)f); }
case 'STR': { string s = lex.sattr; lex.Next(); auto str = g_vm->NewString(s); allocated.push_back(str); return Value(str); }
case 'NIL': { lex.Next(); return Value(0, V_NIL); }
case '-':
{
lex.Next();
Value v = ParseFactor();
switch (v.type)
{
case V_INT: v.ival *= -1; break;
case V_FLOAT: v.fval *= -1; break;
default: lex.Error("numeric value expected");
}
return v;
}
case '[':
{
lex.Next();
Gobble('LF');
vector<Value> elems;
if (lex.token == ']') lex.Next();
else
{
for (;;)
{
elems.push_back(ParseFactor());
bool haslf = lex.token == 'LF';
if (haslf) lex.Next();
if (lex.token == ']') break;
if (!haslf) Expect(',');
}
lex.Next();
}
int type = -1;
if (lex.token == ':')
{
lex.Next();
string sname = lex.sattr;
Expect('ID');
size_t reqargs = 0;
int idx = g_vm->StructIdx(sname, reqargs);
if (idx >= 0) // if unknown type, becomes regular vector
{
while (elems.size() < reqargs) { elems.push_back(Value(0, V_NIL)); } // pad with NIL if current type has more fields
while (elems.size() > reqargs) { elems.back().DEC(); elems.pop_back(); } // drop elements if current type has less fields
type = idx;
}
}
auto vec = g_vm->NewVector(elems.size(), type);
allocated.push_back(vec);
for (auto &e : elems) vec->push(e.INC());
return Value(vec);
}
default:
lex.Error("illegal start of expression: " + lex.TokStr());
return Value();
}
}