Re: Hello, How to parse lists?

On 30-10-16 00:29, Jens Kallup wrote:
> parameter =  alpha.input("parameter") > def_param
> def_param =  alpha.input(alpha) |
>              (alpha.input(alpha) > ',' > def_param)
> alpha = [a-zA-Z_][a-zA-Z0-9_]

Finally something we can work with. (remember I've asked for SSCCE or
goals for weeks).

Here's the simplest translation of the above:

        ident = qi::char_("a-zA-Z_") >> qi::char_("a-zA-Z0-9_");
        parameter = qi::lexeme["parameter"] >> (ident % ',');

First off, I think `alpha` should be `[a-zA-Z_][a-zA-Z0-9_]...` since
otherwise fff wouldn't match (too many characters)

        ident = qi::char_("a-zA-Z_") >> *qi::char_("a-zA-Z0-9_");

Now it parses the test cases from your earlier mail
<http://coliru.stacked-crooked.com/a/e95fd41d4d4fe4a5>:

    ===== input 'parameter fff'

    Ok: 1

    Ident: fff

    ===== input 'parameter fff , ccc'

    Ok: 2

    Ident: fff

    Ident: ccc

    ===== input 'parameter fff, ccc ddd ddd dd dd'

    Ok: 2

    Ident: fff

    Ident: ccc

    Remaining unparsed: 'ddd ddd dd dd'...

Now you wish for the last one to "fail"? I presume that might be because
end of input has not been reached. You can either check that the end
iterator is reached, or add `>> qi::eoi` to ensure that EOI
(end-of-input) was reached:

        parameter = qi::lexeme["parameter"] >> (ident % ',') >> qi::eoi;

Then the output becomes
<http://coliru.stacked-crooked.com/a/95c7f4a181ff0713>:

    ===== input 'parameter fff'

    Ok: 1

    Ident: fff

    ===== input 'parameter fff , ccc'

    Ok: 2

    Ident: fff

    Ident: ccc

    ===== input 'parameter fff, ccc ddd ddd dd dd'

    Fail

    Remaining unparsed: 'parameter fff, ccc ddd ddd dd dd'...

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