From @smls

S05 <http://design.perl6.org/S05.html#line_2234> says​:

  Backslash escapes for literal characters in ordinary strings are
  allowed in regexes (\a, \x, etc.). However, the exception to this
  rule is \b, which is disallowed in order to avoid conflict with
  its former use as a word boundary assertion. To match a literal
  backspace, use \c8, \x8, or a double-quoted \b.

I found out the hard way today why that second sentence was specced, when I puzzled over a regex of mine for several minutes before I realized that the reason it didn't match, was that I had written my word boundaries as `\b` (Perl/GNU/.NET regex syntax) instead of `<|w>` (Perl 6 regex syntax).

From @zoffixznet

+1

This can't be added in 6.c, however.

From @zoffixznet

Listed self as steakholder to implement this in 6.d​: Raku/old-design-docs@b14828bb01

From @pmichaud

I don't quite understand what is meant by "This can't be added in 6.c, however" above.

If it's intended to mean "We can't add this to the 6.c language spec" (because it was released in December), then I pretty much agree with that.

But if it's intended to mean "We can't change this behavior in Rakudo until we update the spec", I disagree.

The 6.c spec (what is in roast) doesn't appear to have any tests for \b in regexes, which (to me) means the behavior of \b is undefined (or undertested) in 6.c. I don't think it should mean that Rakudo's current behavior is the 6.c behavior.

Furthermore, given that S05 has (for a couple of years) already explicitly called out \b as being forbidden, this looks to me like a run-of-the-mill rakudobug that simply needs a corrected implementation and corresponding tests added to roast. And adding the tests into roast will automatically makes it part of the 6.d spec.

Or am I missing something entirely?

Pm

On Wed Aug 24 11​:04​:41 2016, cpan@​zoffix.com wrote​:

Listed self as steakholder to implement this in 6.d​:
Raku/old-design-docs@b14828bb01

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

From @zoffixznet

Per comments on [^1], this ticket can be resolved right now, without waiting for 6.d

[1] Raku/old-design-docs@b14828b#commitcomment-18777938

From @zoffixznet

On Thu, 18 Aug 2016 10​:27​:04 -0700, smls75@​gmail.com wrote​:

S05 <http://design.perl6.org/S05.html#line_2234> says​:

Backslash escapes for literal characters in ordinary strings are
allowed in regexes (\a, \x, etc.). However, the exception to this
rule is \b, which is disallowed in order to avoid conflict with
its former use as a word boundary assertion. To match a literal
backspace, use \c8, \x8, or a double-quoted \b.

I found out the hard way today why that second sentence was specced,
when I puzzled over a regex of mine for several minutes before I
realized that the reason it didn't match, was that I had written my
word boundaries as `\b` (Perl/GNU/.NET regex syntax) instead of `<|w>`
(Perl 6 regex syntax).

Thanks for the report. This is now fixed \o/

Fix commits​:
Raku/nqp@c5f38888ec
Raku/nqp@66308ea63d
rakudo/rakudo@08589d32fa

Tests​: Raku/roast@846af2a582

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