Since the parser is recursive parse_* methods (in particular,
parse_binop_rhs()) does NOT check if the last unparsed token is valid.
Thus parse_expression() stops if it encounters an unknown token. That's
why parser::operator() needs to make sure nothing is left in the input
stream.
+/// parser happily accepted various junk like 'x^2()+1'
+static int check4(std::ostream& err_str)
+{
+ const std::string junk("x^2()+1");
+ parser reader;
+ ex e;
+ try {
+ e = reader(junk);
+ err_str << "parser accepts junk: \"" << junk << "\"" << std::endl;
+ return 1;
+ } catch (parse_error& err) {
+ // Ok, parser rejects the nonsense.
+ return 0;
+ }
+}
+
int main(int argc, char** argv)
{
std::cout << "checking for parser bugs. " << std::flush;
int main(int argc, char** argv)
{
std::cout << "checking for parser bugs. " << std::flush;
errors += check1(err_str);
errors += check2(err_str);
errors += check3(err_str);
errors += check1(err_str);
errors += check2(err_str);
errors += check3(err_str);
+ errors += check4(err_str);
if (errors) {
std::cout << "Yes, unfortunately:" << std::endl;
std::cout << err_str.str();
if (errors) {
std::cout << "Yes, unfortunately:" << std::endl;
std::cout << err_str.str();
scanner->switch_input(&input);
get_next_tok();
ex ret = parse_expression();
scanner->switch_input(&input);
get_next_tok();
ex ret = parse_expression();
+ // parse_expression() stops if it encounters an unknown token.
+ // This is not a bug: since the parser is recursive checking
+ // whether the next token is valid is responsibility of the caller.
+ // Hence make sure nothing is left in the stream:
+ if (token != lexer::token_type::eof)
+ Parse_error("expected EOF");
+