[DGD] parse_string

[Mikael Lind]

Hello,

2007/2/19, chris . <psych_mayo at hotmail.com>:
> I have 2 questions.  First, I am trying to make what should be a real easy
> auto-fun.  It would check to see if str2 contains str.  If yes return 1, if
> no return 0.  I am getting an error, and would like to know where i am going
> wrong (aside from not understanding compiler-ish).

You did not specify the error message, but I am guessing that it is a
tokenizing error. You define a token for your pattern, but there is no
token for anything else that could be in the searched string.
parse_string() allows you to define a nomatch token, that will match
anything else. You define it like this:

dummy = nomatch

Noah Gibbs has compiled some documentation and posts on parse_string():

http://phantasmal.sourceforge.net/DGD/Programming/Parse_String.html

There are some other problems with your code as well. Can you trust
the search string? What happens if it contains a token delimiter
(slash)? Also remember that tokens are regular expression, so if you
want a plain substring match, you may get unexpected results if the
search string contains characters that have a special meaning in
regular expressions.

If you want a plain substring match, I would go with explode() or
sscanf() instead of parse_string(). I expect a sscanf-based solution
to be more efficient, but slightly more complex because you need to
escape percent signs in the substring.

explode()-based solution:

int searchstr(string str,string str2) {
    return sizeof(explode(str + str2 + str, str)) >= 2;
}

sscanf()-based solution:

int searchstr(string str,string str2) {
    if (sscanf(str, "%*s%%") != 0) {
        /* escape all % in substring */
        str = implode(explode("%" + str + "%", "%"), "%%");
    }
    return sscanf(str2, "%*s" + str) != 0;
}

(The code above is untested.)

> My second question: This stuff seems like it can go pretty deep, and it
> would take a lot of effort for me to get out in the deep end.  I am not
> seeing myself writing complex parsers for player input.  Should I bother
> myself to pick up a textbook on compiler-ish, or in my situation does the
> effort outweigh the benefits?

The parser is powerful and is not limited to parsing player commands,
though it is probably overkill for this specific problem.

Regards,
Mikael