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Re: Perl 5.18 and Regexp::Grammars
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From:
demerphq
Date:
August 13, 2013 15:05
Subject:
Re: Perl 5.18 and Regexp::Grammars
Message ID:
CANgJU+U7_tFyAJwMRVJiAsJuvGzmdrB6c28A7A9HvNJyG0Btfg@mail.gmail.com
On 13 August 2013 15:52, Dave Mitchell <davem@iabyn.com> wrote:
> On Mon, Aug 12, 2013 at 08:04:17PM +0200, Aristotle Pagaltzis wrote:
>> * demerphq <demerphq@gmail.com> [2013-08-12 15:40]:
>> > I think he means something like this:
>> >
>> > source( $quote, $start_delim1, $end_delim1, $modifiers, $text1,
>> > $start_delim2, $end_delim2, $text2 );
>
>
> Ah I see. Yes, I had envisioned something like that.
>
> The one major way I suspect I may need to deviate from that is that I
> would expect that for tr/// and s///, for the 'source' method to be called
> twice, once for the src pattern and once for replacement (with presumably
> an indication of whether it's first or second), so there wouldn't be foo2
> args.
>
> I don't know whether that would be a big limitation. It implies that any
> modifications to 'src' in s/src/dst/ and tr/src/dst/ has has to be done
> before the code has a chance to 'dst'.
>
> Doing it otherwise would, I suspect be a lot harder. There is currently a
> function, S_scan_str() which basically extracts out a single-quotish value
> while processing just \-delimiter; this string may be left as-is,
> or passed on for double-quotish parsing. Making S_scan_str() check for
> an overloaded source method and calling it before returning is
> (relatively) simple. Something like s/// causes S_scan_str() to be called
> twice. Somehow saving the results of two calls to S_scan_str() then
> calling source() once would, I suspect, be trickier.
>
> In terms of other semantics, I'm assuming that the value returned by
> source() will be immediately stringified then used in place of the
> original text (so if source() returns an overloaded or regex object, it
> wont stay that way).
>
> Exactly how \ and escaped delimiters are handled needs to be decided, but
> I suspect that that will be largely determined by how S_scan_str() already
> operates.
>
> So in something like
>
> 'ab\\c\'d'
>
> I'd expect source() to be called with (amongst other things), a string
> consisting of the 7 chars
>
> a b \ \ c ' d
>
> (Note that in single-quoted strings, double-\ stripping is done later).
>
> But I think largely the details don't matter as long as they are clearly
> documented (like that source() needs to return a double-\ if it is to be
> interpreted as a \ ).
>
> So, apart from the devil of the details, does anyone have any strong
> feeling pro- or anti- this proposal?
I am pro. Although perhaps not strongly enough to reply.
Yves
--
perl -Mre=debug -e "/just|another|perl|hacker/"
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