static double factor()
{
if (follows(MT_BRA))
{
next_token();
MItem* it = expression();
if (it->n >= 0)
serror("invalid use of list.");
if (!follows(MT_KET))
serror("')' expected.");
next_token();
return it->val;
}
else if (follows(MT_NUMBER))
{
double val = token->value;
next_token();
return val;
}
else if (follows(MT_IDENT))
{
MSymbol* sym = peek_symbol(token->text);
if (sym == NULL)
serror("unknown identifier '%s'.", token->text);
next_token();
if (follows(MT_BRA))
{
if (sym->built_in == NULL)
serror("unknown function '%s'.", sym->name);
next_token();
return eval_fn(sym);
}
else
{
if (sym->built_in != NULL)
serror("invalid use of function.");
if (sym->data->n >= 0)
serror("invalid use of list.");
return sym->data->val;
}
}
else {
serror("syntax error: '%s'", token->text);
return 0.0;
}
}
static MItem* expression()
{
// special case: expression is a list reference
if (follows(MT_IDENT))
{
MSymbol* list = peek_symbol(token->text);
if (list != NULL && list->built_in == NULL &&
list->data != NULL && list->data->n >= 0)
{
next_token();
// only "=", "}", ";" or "," must follow
if (!follows(MT_EQUAL) && !follows(MT_END) &&
!follows(MT_COMMA) && !follows(MT_SEMICOL))
serror("invalid use of list.");
return list->data;
}
}
// handle unary + and -
double unary = 1.0;
if (follows(MT_PLUS) || follows(MT_MINUS))
{
if (follows(MT_MINUS)) unary = -1.0;
next_token();
}
double result = unary * term();
while (follows(MT_PLUS) || follows(MT_MINUS))
{
if (follows(MT_PLUS)) { next_token(); result += term(); }
else { next_token(); result -= term(); }
}
MItem* it = new_item();
it->n = -1;
it->val = result;
return it;
}
MSymbol* mesh_parser_find_symbol(const char* name)
{
return peek_symbol(name);
}
