Re: Why token are numbered from 258?
Akim Demaille <[email protected]>
| Newsgroups | gmane.comp.parsers.bison.general |
|---|---|
| Message-ID | <[email protected]> |
> Le 7 févr. 2019 à 18:33, Peng Yu <[email protected]> a écrit : > > Hi, > > I don't quite understand why tokens are numbered starting from 258. > What are 256 and 257 for? Thanks. > > #define IF 258 256 is the error token, and 257 is the undef token (when we receive unknown tokens from yylex). 256 is mandated by POSIX : https://pubs.opengroup.org/onlinepubs/007904875/utilities/yacc.html > The token error shall be reserved for error handling. The name error can be used in grammar rules. It indicates places where the parser can recover from a syntax error. The default value of error shall be 256. Its value can be changed using a %token declaration. The lexical analyzer should not return the value of error. It seems to say that we should be able to change the value with `%token error 2400`, but we don't support that. (checking...) OMG, we do support it! New test case... _______________________________________________ [email protected] https://lists.gnu.org/mailman/listinfo/help-bison