I'm using Lemon as a parser generator, its error handling is the same as yacc's and bison's if you don't know Lemon.
Lemon has an option to define the error token in a set of rules in order to catch parsing errors. The default behavior of the generated parser is to destroy the token causing the error; is there any way to override this behavior so that I can keep the token?
Here's an example to show what's happening: basically I'm appending the tokens for each rule together to reform the input string, here's an example grammar:
input ::= string(A) { printf("%s", A); } // Print the result
string(A) ::= string(B) part(C). { A = append(B, C); }
string(A) ::= part(B). { A = B; }
part(A) ::= NUMBER(B) NAME(C). { A = append(C, B); } // Rearrange the number and name
part(A) ::= error(B). { A = B; } // On error keep the token anyways
On input:
"Username 1234Joseph"
I get output:
"Joseph1234"
Because the text "Username " is junked by the parser in the part(A) ::= error(B) rule, but I really want:
"Username Joseph1234"
as output.
If you can solve this problem in bison or another parser generator I would accept that as an answer :)