Re: generating grammars, capturing in regex interpolation, etc.

[Nathan Gray]

On Wed, Apr 15, 2015 at 09:45:39PM -0400, Nathan Gray wrote:
> I had given up on using regexes embedded within regexes, because
> I could not get capturing to work.

I did a backtrace on one of the test cases that fails, which led
me to

  src/core/Cursor.pm

in

  method INTERPOLATE(\var, $i = 0, $s = 0, $a = 0)

with this comment:

  # Call it if it is a routine. This will capture if requested.
  return (var)(self) if nqp::istype(var,Callable);

This seems to indicate that captures in the embedded regexes
should capture.

When the capture does not happen, is this a bug?

The test cases I came up with, that illustrate capturing from
embedded regexes (some which work, some which do not), are
included below.

-kolibrie

use v6;
use Test;

my $year = '2015';
my $month = '04';
my $day = '11';
my $date_string = "$year-$month-$day";

my $year_regex = rx/$<year>=[\d**4]/;
my $month_regex = rx/$<month>=[\d\d?]/;
my $day_regex = rx/$<day>=[\d\d?]/;
my $separator = rx/'-'/;

# Single named capture.
{
    ok($date_string ~~ $year_regex, 'date string matches year regex');
    is(~$/, $year, 'matched is year string');
    is(~$/<year>, $year, 'year is captured');
}

# Single named capture in slashes.
{
    ok($date_string ~~ /$year_regex/, 'date string matches year regex when in 
slashes');
    is(~$/, $year, 'matched is year string when in slashes');
    is(~$/<year>, $year, 'year is captured when in slashes');  # Fails
}

# Single named capture embedded in named capture.
{
    ok($date_string ~~ /$<pattern>=$year_regex/, 'date string matches year 
regex when embedded');
    is(~$/, $year, 'matched is year string when embedded');
    is(~$/<pattern>, $year, 'pattern is captured when embedded');
    is(~$/<pattern><year>, $year, 'year is captured when embedded');
}

# Single named capture embedded in named capture with brackets.
{
    ok($date_string ~~ /$<pattern>=[$year_regex]/, 'date string matches year 
regex when embedded with brackets');
    is(~$/, $year, 'matched is year string when embedded with brackets');
    is(~$/<pattern>, $year, 'pattern is captured when embedded with brackets');
    is(~$/<pattern><year>, $year, 'year is captured when embedded with 
brackets');  # Fails
}

# Multiple named captures.
{
    ok($date_string ~~ /$year_regex $separator $month_regex $separator 
$day_regex/, 'date string matches multiple regexes in slashes');
    is(~$/, $date_string, 'matched is date string in multi regex with slashes');
    is(~$/<year>, $year, 'year is captured in multi regex with slashes');  # 
Fails
    is(~$/<month>, $month, 'month is captured in multi regex with slashes');  # 
Fails
    is(~$/<day>, $day, 'day is captured in multi regex with slashes');  # Fails
}

# Multiple named captures embedded in named capture.
{
    ok($date_string ~~ /$<pattern>=$year_regex $separator $month_regex 
$separator $day_regex/, 'date string matches multiple regexes when embedded');
    is(~$/, $date_string, 'matched is date string in multi regex when 
embedded');
    is(~$/<pattern>, $year, 'pattern is captured in multi regex when embedded');
    is(~$/<pattern><year>, $year, 'year is captured in multi regex when 
embedded');
    is(~$/<month>, $month, 'month is captured in multi regex when embedded');  
# Fails
    is(~$/<day>, $day, 'day is captured in multi regex when embedded');  # Fails
}

# Multiple named captures embedded in named capture with brackets.
{
    ok($date_string ~~ /$<pattern>=[$year_regex $separator $month_regex 
$separator $day_regex]/, 'date string matches multiple regexes when embedded 
with brackets');
    is(~$/, $date_string, 'matched is date string in multi regex when embedded 
with brackets');
    is(~$/<pattern>, $date_string, 'pattern is captured in multi regex when 
embedded with brackets');
    is(~$/<pattern><year>, $year, 'year is captured in multi regex when 
embedded with brackets');  # Fails
    is(~$/<pattern><month>, $month, 'month is captured in multi regex when 
embedded with brackets');  # Fails
    is(~$/<pattern><day>, $day, 'day is captured in multi regex when embedded 
with brackets');  # Fails
}

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