Re: generating grammars, capturing in regex interpolation, etc.
Am 17.04.2015 um 04:34 schrieb Nathan Gray:
# 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.
On Fri, Apr 17, 2015 at 09:47:22AM +0200, Tobias Leich wrote:
The comment in INTERPOLATE is about subcaptures... but if you do not
capture the interpolated regex itself, you break that chain.
Is there a way to specify several captures?
For instance, if I build a data structure with information about
how to parse pieces from a string, and want to be able to
construct a regex from those pieces (which pieces I include, and
what order they are in will be specified as late as possible),
what is the best way to capture those pieces by name?
# Static data structure.
my %date_parts = (
year = {
regex = rx/\d**4/,
},
month = {
regex = rx/\d\d?/,
},
day = {
regex = rx=\d\d?/,
},
);
# Some made up routine that illustrates building a regex that captures.
my $regex = build_capturing_regex('year', rx/'-'/, 'month', rx/'-'/, 'day');
# The generated $regex looks like this (or matches the same as this):
rx/
$year=[\d**4] # The name comes from the key in %date_parts, the value
from the regex value.
'-'
$month=[\d\d?]
'-'
$day=[\d\d?]
/;
# Compare a date string to the regex.
my $date_string = '2015-04-20';
my $match = $date_string ~~ $regex;
# The $match contains:
~$matchyear # '2015'
~$matchmonth # '04'
~$matchday # '20'
~$match# '215-04-20'
Is there built-in functionality that does what build_capturing_regex()
illustrates? For instance, if the %date_parts data structure is
re-written as a grammar, is there a way to dynamically specify
how regex TOP is defined? Or is there a different way I could
approach this problem that is easier, or fits better with Perl 6?
If I need to write something like build_capturing_regex(), what
is the syntax to combine several pre-existing regexes into a
single regex, in a way that allows for capturing to occur?
If you've been following this thread, you know that I've tried
every syntax I could think of, plus any others that have been
suggested to me. Matching always works. Capturing a single
value works. I have not been able to figure out how to capture
more than one value from a generated/interpolated/constructed
regex (unless I use strings instead of regexes and then EVAL the
string into a regex, but I think I should avoid that, unless
there's no better way).
-kolibrie
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Re: generating grammars, capturing in regex interpolation, etc.
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The comment in INTERPOLATE is about subcaptures... but if you do not
capture the interpolated regex itself, you break that chain.
Am 17.04.2015 um 04:34 schrieb 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, $year, 'pattern is captured when embedded');
is(~$/patternyear, $year, 'year is captured when embedded');
}
# Single named capture embedded in named capture with brackets.
{
ok($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, $year, 'pattern is captured when embedded with
brackets');
is(~$/patternyear, $year, 'year is captured when embedded with
brackets'); # Fails
}
# Multiple named captures.
{
ok($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, $year, 'pattern is captured in multi regex when
embedded');
is(~$/patternyear, $year, 'year is captured in multi regex
when embedded');
is(~$/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, $date_string, 'pattern is captured in multi regex
when embedded with brackets');
is(~$/patternyear, $year, 'year is captured in multi regex
when embedded with brackets'); # Fails
is(~$/patternmonth, $month, 'month is captured in multi regex
when embedded with brackets'); # Fails
is(~$/patternday, $day, 'day is captured in multi regex when
embedded with brackets'); # Fails
}
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Re: generating grammars, capturing in regex interpolation, etc.
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, $year, 'pattern is captured when embedded');
is(~$/patternyear, $year, 'year is captured when embedded');
}
# Single named capture embedded in named capture with brackets.
{
ok($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, $year, 'pattern is captured when embedded with brackets');
is(~$/patternyear, $year, 'year is captured when embedded with
brackets'); # Fails
}
# Multiple named captures.
{
ok($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, $year, 'pattern is captured in multi regex when embedded');
is(~$/patternyear, $year, 'year is captured in multi regex when
embedded');
is(~$/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, $date_string, 'pattern is captured in multi regex when
embedded with brackets');
is(~$/patternyear, $year, 'year is captured in multi regex when
embedded with brackets'); # Fails
is(~$/patternmonth, $month, 'month is captured in multi regex when
embedded with brackets'); # Fails
is(~$/patternday, $day, 'day is captured in multi regex when embedded
with brackets'); # Fails
}
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Re: generating grammars, capturing in regex interpolation, etc.
On Tue, Apr 14, 2015 at 08:58:27PM -0400, Nathan Gray wrote: I've run into a snag, in that my strptime processing in Perl 5 relies on building a string that looks like a regex with named captures, and then interpolating that into a real regex. [...] my $pattern = Q/$greeting=[hello]/; my $string = Q/hello/; [...] Just an idea: instead of building strings to be interpolated into a regex, could you just build regexes directly? my $pattern = rx/$greeting=[hello]/; my $match = hello ~~ / pattern=$pattern /; The resulting string is captured into $matchpatterngreeting; The second statement can also be written as: # captures into $matchpatterngreeting my $match = hello ~~ / $pattern=$pattern /; # captures into $match[0]greeting my $match = hello ~~ / $0=$pattern /; Hope this is useful, or at least illustrative. Of course, there may be a better way, since regex interpolation seems frowned upon in Perl 6. I think it's more that we treat regexes as first class components (actually closures)... rather than EVALing strings with metacharacters, we just build regex expressions and interpolate them directly. Pm
