On Wed, 8 Dec 2004 08:19:17 -0800, Larry Wall <[EMAIL PROTECTED]> wrote:
> / $<bar> := [ (<?ident>) = (\N+) ]* /
You know, to be honest I don't know that I want rules in one-liners to
capture by default. I certainly want them to capture in rules, though.
> And people would have to get used to seeing ? as non-capturing assertions:
>
> <?before ...>
> <?after ...>
> <?ws>
> <?sp>
> <?null>
>
> This has a rather Ruby-esque "I am a boolean" feeling to it. I think
> I like it. It's pretty easy to type, at least on my keyboard.
I like it. It reads to me as "if before ...", "if null". Sounds good.
> I think I'm leaning toward the idea that anything in angles that
> begins alpha is a capture to just the alpha part, so the ? prefix is
> merely a no-op that happens to make the assertion not start with an
> alpha. Interestingly, that gives these implicit bindings:
>
> <after ...> $<after> $`
> <before ...> $<before> $'
Again, I don't see the utility of that in a one-liner. In a grammar,
you would create a real rule which would assert <after ...> and
capture the result in a reasonable name.
> Anyway, that's where I am this week/day/hour/minute/second.
I'm thinking capturing rules should be default in rules, where they're
downright useful. Your hour/minute/second comment brings up parsing
ISO time:
grammar ISO8601::DateTime {
rule year { \d<4> }
rule month { \d<2> }
rule day { \d<2> }
rule hour { \d<2> }
rule minute { \d<2> }
rule second { \d<2> }
rule fraction { \d+ }
rule date { <year> -? <month> -? <day> }
rule time { <hour> \:? <minute> \:? <second> [\. <fraction>]? }
rule datetime { <date> T <time> }
}
For a grammar, that works perfectly!
In a one-liner, I'd rather just use:
$datetime ~~ /$year := (\d+) -? $month := (\d+) -? ...../
and specify the vars I want to save directly in my own scope.
Ashley Winters
