std.regex named matches

[James Miller]

On 22 February 2012 04:45, Dmitry Olshansky <dmitry.olsh at gmail.com> wrote:
> On 21.02.2012 7:34, James Miller wrote:
>>
>> On 20 February 2012 21:34, Dmitry Olshansky<dmitry.olsh at gmail.com>  wrote:
>>>
>>> 08.02.2012 13:07, James Miller пишет:
>>>
>>>>
>>>> Hi,
>>>>
>>>> I am using std.regex and using the named matches. I would like to be
>>>> able to get at the names that have matched, since this is library
>>>> code.
>>>>
>>>> e.g.
>>>>
>>>>     auto m = match("test/2", regex(r"(?P<word>\w+)/(?P<num>\d)"));
>>>>     //either
>>>>     auto names = m.names;
>>>>     //or
>>>>     auto names = m.captures.names;
>>>>
>>>> or something similar. I've looked at the library and I can't find
>>>> anything of the sort, and you can't even use `foreach` to get at them
>>>> that way, I'm guessing because you can have both integer and string
>>>> indexes for the matches.
>>>>
>>>
>>> I know this is two weeks old, but you can do foreach on them:
>>> foreach(c; m.captures){
>>>        //c is each captured group in turn, the first one is the whole
>>> match
>>> }
>>>
>>>> Thanks
>>>>
>>>> James Miller
>>>
>>>
>>>
>>
>> Yeah, the problem with that is that I want the /names/ of the matches,
>> that only returns the match. This was for library code, so the
>> developer passes the regex. There are workarounds, but I would have
>> liked to be able to do something more like
>>
>>     auto names = m.captures.names;
>>     foreach (name; names) {
>>        writeln(name,": ", m.captures[name]);
>>     }
>>
>> or even a straight AA-style foreach like this:
>>
>>     foreach (name, match; m.captures) {
>>        writeln(name,": ", match);
>>     }
>>
>
> Names work as aliases for numbers, so that not every captured group has
> name. But something along the lines of :
> foreach(num, match; m.captures)
>        writeln(m.nameOf(num),": ",match);
>
> where nameOf(x) should return mm.. empty string for groups with no name?
>
>
>> it was decided that more data was needed in regex anyway, but there
>> was no consensus as to how that should be implemented.
>
>
> Yes, more thought work needed. And being the guy behind current
> implementation, I'm curious what's your use case and how to best fit it in
> general API.
>
> --
> Dmitry Olshansky

Ah, right, nameOf would work ok. I know that the issue stems from
there not really being a "best-solution" in this case because of the
fact that you can have named /and/ unnamed matches.

I don't /require/ it, it just would make my life easier.

My use case, expanding on what I said before, is that I want to be
able to present debugging information, being able to enumerate the
names in the match goes a long way to that.

Also it means I can do more flexible dispatching of data, otherwise I
need hardcoded rules for the names, which is unfortunate.

Like I said, nothing wrong with what is there, I just think that it
can be improved.

nameOf would work well, if it returns null, or empty string, then
there is no name for that match. Since you can already grab specific
names out of the regex anyway, this just fills in the gap in the other
direction, going from match to name, rather than name to match.

Thanks
--
James Miller