everyone!
I want to use boost::spirit to parse some string in text file.
Here is the sample in the text file:
IF([banana] and [apple] and [yellow] or [green] or [red] and [!white])
THEN
do sth...;
ELSE
do sth...;
When i parse the string in the "if" bracket i got a trouble.
Here is my code:
if_rule=str_p(IF)>>ch_p("(")>>if_mem>>*("and"|"or">>if_mem)>>ch_p(")");
if_mem=ch_p("[")>>*~ch_p("]")>>ch_p("]");
It dose not work.It just parse the two "and" of the beginning and ignore the "or".
I've try several different grammer and still didn't work.
Thank you for your help!
You need to keep in mind that ultimately a Spirit expression is simply a (really ugly) c++ expression and thus it must follow c++ rules. Independently of the meaning that Spirit gives to the operators, they still follow c++ operator precedence rules. And so the expression "and" | "or" >> if_mem is not the same as ("and" or "or") followed by if_mem but in fact is "and" or ("or" followed by if_mem) since >> has a higher precedence than |. If you use ("and"|"or")>>if_mem you face another separate problem: since none of its arguments is a Spirit expression, the operator | is not the alternative parser, but the default c++ bitwise_or operator and that, as you discovered, causes a compiler error. The solution in this case is to make at least one of the arguments a Spirit expression by using (I'm just guessing since I don't use Spirit.Classic) something like (str_p("and")|str_p("or"))>>if_mem. (I guess "and">>if_mem | "or">>if_mem should also work, but it's probably a worse alternative).
As sehe points in his comment, if you have a choice (unless you need to work with legacy code basically) you should probably use Spirit v2 since it will be far easier to get help.