Bison one or more occurrences in grammar file

Question

My program that needs to be parsed should be of the form:

program   : [declaration]+
          ;

Which should mean: The program consists of one or more declarations. Declaration on its turn is of course defined in a similar way, and so on...

Currently, I'm getting an error on the + from the Bison parser. How do I define the one or more condition in a correct way with bison?

score 22 · Accepted Answer · answered Mar 24 '15 at 15:28

22

One or more:

declarations
    : declaration
    | declarations declaration
    ;

Zero or more:

declarations
    : /* empty */
    | declarations declaration
    ;

answered Mar 24 '15 at 15:28

user207421

voluminat0 · Answer 2 · 2015-03-24T16:13:08.663

-1

Apparently,

Bison does not support the + or * symbols to denote these things.

How I solved it:

program     : declarations
        ;

declarations    : declaration declarations
        | declaration
        ;

edited Mar 24 '15 at 16:13

answered Mar 24 '15 at 15:12

voluminat0

1

That's not one or more, that's zero or more. For one or more you want to replace `/* empty */` with declaration. – sepp2k Mar 24 '15 at 15:26
1

This solution is right-recursive, which is not the correct way to use an LALR(1) parser. It should be left-recursive. – user207421 Jun 21 '19 at 11:45

2 Answers2