Behavior of Regular Expressions Contained in a Constant with a Sigil

[p6rt]

Migrated from rt.perl.org#127352 (status was 'resolved')

Searchable as RT127352$

[p6rt]

From jpolanik@nc.rr.com

Constants are not required to have a sigil but apparently they may.

Unfortunately, when a constant with a sigil contains a regex pattern,
unpredictable results may occur.

The attached file show that a regex pattern that should detect the file
system separator ('/' or '\') yield incorrect results when contained in
a constant whose names contains a sigil but correct results otherwise.

Identical results were obtained on Linux (Ubuntu 12.04) and Mac OS X 10.10.5

Build information

Linux

$ perl6 -version
This is Rakudo version 2015.12 built on MoarVM version 2015.12
implementing Perl 6.c.

Mac

$ perl6 -version
This is Rakudo version 2015.12-176-gaefe2c2 built on MoarVM version
2015.12-29-g8079ca5 implementing Perl 6.c.

Thanks,

Joseph Polanik

[p6rt]

From jpolanik@nc.rr.com

#!/usr/bin/env perl6

# Constants are not required to have a sigil. When they have a sigil and
# contain a regex, the results are unpredictable.

constant $sepreg = /(<[\\\/]>)/;
my $sepreg2 = /(<[\\\/]>)/;
constant sepreg3 = /(<[\\\/]>)/;

my $filenameW = "c​:\\g\\b.mp4";
my $filenameL = "/g/b.mp4";

say "============= Looking for a Windows separator​: \\";
# The match is made but $/ doesn't get populated
say "Testing regex as a constant with a sigil​: Windows separator";
if ($filenameW ~~ $sepreg) {
  say $/[0].Str;
}
else {
  say "No match for SEP";
}

# Gives correct result
say "Testing regex as a constant with no sigil​: Windows separator";
if ($filenameW ~~ sepreg3) {
  say $/[0].Str;
}
else {
  say "No match for SEP";
}

# Gives correct result
say "Testing regex as a lexical variable​: Windows separator";
if ($filenameW ~~ $sepreg2) {
  say $/[0].Str;
}
else {
  say "No match for SEP";
}

# Gives correct result
say "Testing regex as a string​: Windows separator";
if ($filenameW ~~ /(<[\\\/]>)/) {
  say $/[0].Str;
}

#
# Now try the same tests with a *nix file system
#
say "============= Looking for a *nix separator​: /";

# The match is made but $/ doesn't get populated
say "Testing regex as a constant with a sigil​: *nix separator​: Wrong Result";
if ($filenameL ~~ $sepreg) {
  say $/[0].Str;
}
else {
  say "No match for SEP";
}

# Gives correct result
say "Testing regex as a constant with no sigil​: *nix separator";
if ($filenameL ~~ sepreg3) {
  say $/[0].Str;
}
else {
  say "No match for SEP";
}

# Gives correct result
say "Testing regex as a lexical variable​: *nix separator";
if ($filenameL ~~ $sepreg2) {
  say $/[0].Str;
}
else {
  say "No match for SEP";
}

# Gives correct result
say "Testing regex as a string​: *nix separator";
if ($filenameL ~~ /(<[\\\/]>)/) {
  say $/[0].Str;
}

[p6rt]

From @zoffixznet

Still present today​:

<Zoffix> m​: my $sepreg = rx/(<[\\/]>)/; my $filenameW = "c​:\\g\\b.mp4"; $filenameW ~~ $sepreg; say $/;
<camelia> rakudo-moar 589061​: OUTPUT«｢\｣␤ 0 => ｢\｣␤»
<Zoffix> m​: constant $sepreg = rx/(<[\\/]>)/; my $filenameW = "c​:\\g\\b.mp4"; $filenameW ~~ $sepreg; say $/;
<camelia> rakudo-moar 589061​: OUTPUT«Nil␤»
<Zoffix> m​: constant sepreg = rx/(<[\\/]>)/; my $filenameW = "c​:\\g\\b.mp4"; $filenameW ~~ sepreg; say $/;
<camelia> rakudo-moar 589061​: OUTPUT«｢\｣␤ 0 => ｢\｣␤»

[p6rt]

From @dogbert17

On Fri, 05 Aug 2016 18​:04​:36 -0700, cpan@​zoffix.com wrote​:

Still present today​:

<Zoffix> m​: my $sepreg = rx/(<[\\/]>)/; my $filenameW =
"c​:\\g\\b.mp4"; $filenameW ~~ $sepreg; say $/;
<camelia> rakudo-moar 589061​: OUTPUT«｢\｣␤ 0 => ｢\｣␤»
<Zoffix> m​: constant $sepreg = rx/(<[\\/]>)/; my $filenameW =
"c​:\\g\\b.mp4"; $filenameW ~~ $sepreg; say $/;
<camelia> rakudo-moar 589061​: OUTPUT«Nil␤»
<Zoffix> m​: constant sepreg = rx/(<[\\/]>)/; my $filenameW =
"c​:\\g\\b.mp4"; $filenameW ~~ sepreg; say $/;
<camelia> rakudo-moar 589061​: OUTPUT«｢\｣␤ 0 => ｢\｣␤»

Fixed with commit rakudo/rakudo@5ac593e

[p6rt]

The RT System itself - Status changed from 'new' to 'open'

[p6rt]

From @dogbert17

On Tue, 13 Mar 2018 14​:50​:17 -0700, jan-olof.hendig@​bredband.net wrote​:

On Fri, 05 Aug 2016 18​:04​:36 -0700, cpan@​zoffix.com wrote​:

Still present today​:

<Zoffix> m​: my $sepreg = rx/(<[\\/]>)/; my $filenameW =
"c​:\\g\\b.mp4"; $filenameW ~~ $sepreg; say $/;
<camelia> rakudo-moar 589061​: OUTPUT«｢\｣␤ 0 => ｢\｣␤»
<Zoffix> m​: constant $sepreg = rx/(<[\\/]>)/; my $filenameW =
"c​:\\g\\b.mp4"; $filenameW ~~ $sepreg; say $/;
<camelia> rakudo-moar 589061​: OUTPUT«Nil␤»
<Zoffix> m​: constant sepreg = rx/(<[\\/]>)/; my $filenameW =
"c​:\\g\\b.mp4"; $filenameW ~~ sepreg; say $/;
<camelia> rakudo-moar 589061​: OUTPUT«｢\｣␤ 0 => ｢\｣␤»

Fixed with commit
rakudo/rakudo@5ac593e

Roast test added with commit Raku/roast@f2d422f

[p6rt]

@dogbert17 - Status changed from 'open' to 'resolved'