Er, by wfm I mean it matches ｢Is｣ as the code suggests.
On Wed, Mar 17, 2021 at 10:32 PM Ralph Mellor <ralphdjmel...@gmail.com> wrote: > > Works for me in Rakudo 2020.12. > > On Wed, Mar 17, 2021 at 9:33 PM yary <not....@gmail.com> wrote: > > > > The "Interpolation" section of the raku docs use strings as the elements of > > building up a larger regex from smaller pieces, but the example that looks > > fruitful isn't working in my raku. This is taken from > > https://docs.raku.org/language/regexes#Regex_interpolation > > > > > my $string = 'Is this a regex or a string: 123\w+False$pattern1 ?'; > > > > Is this a regex or a string: 123\w+False$pattern1 ? > > > > > my $regex = /\w+/; > > > > /\w+/ > > > > > say $string.match: / $regex /; > > > > Regex object coerced to string (please use .gist or .raku to do that) > > > > ... and more error lines, and no result when the docs show matching '123': > > > > ｢｣ > > > > > > $ raku -v > > > > Welcome to 𝐑𝐚𝐤𝐮𝐝𝐨™ v2020.10. > > > > Implementing the 𝐑𝐚𝐤𝐮™ programming language v6.d. > > > > Built on MoarVM version 2020.10. > > > > > > > > -y > > > > > > On Wed, Mar 17, 2021 at 3:17 PM William Michels via perl6-users > > <perl6-us...@perl.org> wrote: > >> > >> Dear Brad, > >> > >> 1. The list you posted is fantastic ("If the first character inside is > >> anything other than an alpha it doesn't capture"). It should be added to > >> the Raku Docs ASAP. > >> > >> 2. There are some shortcuts that don't seem to follow a set pattern. For > >> example a named capture can be accessed using $<myname> instead of > >> $/<myname> ; the "/' can be elided. Do you have a method you can share for > >> remembering these sorts of shortcuts? Or are they disfavored? > >> > >> > say ~$<myname> if 'abc' ~~ / $<myname> = [ \w+ ] /; > >> abc > >> > > >> [ Above from the example at https://docs.raku.org/syntax/Named%20captures > >> ]. > >> > >> 3. Finally, I've never seen in the Perl6/Raku literature the motto you > >> cite: "One of the mottos of Raku, is that it is ok to confuse a new > >> programmer, it is not ok to confuse an expert." Do you have a citation? > >> > >> [ The motto I prefer is from Larry Wall: "...easy things should stay easy, > >> hard things should get easier, and impossible things should get hard... ." > >> Citation: https://www.perl.com/pub/2000/10/23/soto2000.html/ ]. > >> > >> Best Regards, > >> > >> Bill. > >> > >> > >> > >> On Sat, Mar 13, 2021 at 4:47 PM Brad Gilbert <b2gi...@gmail.com> wrote: > >>> > >>> It makes <…> more consistent precisely because <$pattern> doesn't capture. > >>> > >>> If the first character inside is anything other than an alpha it doesn't > >>> capture. > >>> Which is a very simple description of when it captures. > >>> > >>> <?before …> doesn't capture because of the ｢?｣ > >>> <!before …> doesn't capture because of the ｢!｣ > >>> <.ws> doesn't capture because of the ｢.｣ > >>> <&ws> doesn't capture because of the ｢&｣ > >>> <$pattern> doesn't capture because of the ｢$｣ > >>> <$0> doesn't capture because of the ｢$｣ > >>> <@a> doesn't capture because of the ｢@｣ > >>> <[…]> doesn't capture because of the ｢[｣ > >>> <-[…]> doesn't capture because of the ｢-] > >>> <:Ll> doesn't capture because of the ｢:｣ > >>> > >>> For most of those, you don't actually want it to capture. > >>> With ｢.｣ the whole point is that it doesn't capture. > >>> > >>> <digit> does capture because it starts with an alpha > >>> <pattern=$pattern> does capture because it starts with an alpha > >>> > >>> $0 = <$pattern> doesn't capture to $<pattern>, but does capture to $0 > >>> $<pattern> = <$pattern> captures because of $<pattern> = > >>> > >>> It would be a mistake to just make <$pattern> capture. > >>> Consistency is perhaps Raku's most important feature. > >>> > >>> One of the mottos of Raku, is that it is ok to confuse a new programmer, > >>> it is not ok to confuse an expert. > >>> An expert in Raku understands the deep fundamental ways that Raku is > >>> consistent. > >>> So breaking consistency should be very carefully considered. > >>> > >>> In this case, there is very little benefit. > >>> Even worse, you then have to come up with some new syntax to prevent it > >>> from capturing when you don't want it to. > >>> That new syntax wouldn't be as guessible as it currently is. Which again > >>> would confuse experts. > >>> > >>> If anyone seriously suggests such a change, I will vehemently fight to > >>> prevent it from happening. > >>> > >>> I would be more likely to accept <=$pattern> being added as a synonym to > >>> <pattern=$pattern>. > >>> > >>> On Sat, Mar 13, 2021 at 3:30 PM Joseph Brenner <doom...@gmail.com> wrote: > >>>> > >>>> Thanks much for your answer on this. I think this is the sort of > >>>> trick I was looking for: > >>>> > >>>> Brad Gilbert<b2gi...@gmail.com> wrote: > >>>> > >>>> > You can put it back in as a named > >>>> > >>>> > > $input ~~ / <pattern=$pattern> > >>>> > ｢9 million｣ > >>>> > pattern => ｢9 million｣ > >>>> > 0 => ｢9｣ > >>>> > 1 => ｢million｣ > >>>> > >>>> That's good enough, I guess, though you need to know about the > >>>> issue... is there some reason it shouldn't happen automatically, > >>>> using the variable name to label the captures? > >>>> > >>>> I don't think this particular gotcha is all that well > >>>> documented, though I guess there's a reference to this being a > >>>> "known trap" in the documentation under "Regex interpolation"-- > >>>> but that's the sort of remark that makes sense only after you know > >>>> what its talking about. > >>>> > >>>> I have to say, my first reaction was something like "if they > >>>> couldn't get this working right, why did they put it in?" > >>>> > >>>> > >>>> On 3/11/21, Brad Gilbert <b2gi...@gmail.com> wrote: > >>>> > If you interpolate a regex, it is a sub regex. > >>>> > > >>>> > If you have something like a sigil, then the match data structure gets > >>>> > thrown away. > >>>> > > >>>> > You can put it back in as a named > >>>> > > >>>> > > $input ~~ / <pattern=$pattern> > >>>> > ｢9 million｣ > >>>> > pattern => ｢9 million｣ > >>>> > 0 => ｢9｣ > >>>> > 1 => ｢million｣ > >>>> > > >>>> > Or as a numbered: > >>>> > > >>>> > > $input ~~ / $0 = <$pattern> > >>>> > ｢9 million｣ > >>>> > 0 => ｢9 million｣ > >>>> > 0 => ｢9｣ > >>>> > 1 => ｢million｣ > >>>> > > >>>> > Or put it in as a lexical regex > >>>> > > >>>> > > my regex pattern { (\d+) \s+ (\w+) } > >>>> > > $input ~~ / <pattern> / > >>>> > ｢9 million｣ > >>>> > pattern => ｢9 million｣ > >>>> > 0 => ｢9｣ > >>>> > 1 => ｢million｣ > >>>> > > >>>> > Or just use it as the whole regex > >>>> > > >>>> > > $input ~~ $pattern # variable > >>>> > ｢9 million｣ > >>>> > 0 => ｢9｣ > >>>> > 1 => ｢million｣ > >>>> > > >>>> > > $input ~~ &pattern # my regex pattern /…/ > >>>> > ｢9 million｣ > >>>> > 0 => ｢9｣ > >>>> > 1 => ｢million｣ > >>>> > > >>>> > On Thu, Mar 11, 2021 at 2:29 AM Joseph Brenner <doom...@gmail.com> > >>>> > wrote: > >>>> > > >>>> >> Does this behavior make sense to anyone? When you've got a regex > >>>> >> with captures in it, the captures don't work if the regex is > >>>> >> stashed in a variable and then interpolated into a regex. > >>>> >> > >>>> >> Do capture groups need to be defined at the top level where the > >>>> >> regex is used? > >>>> >> > >>>> >> { # From a code example in the "Parsing" book by Moritz Lenz, p. 48, > >>>> >> section 5.2 > >>>> >> my $input = 'There are 9 million bicycles in beijing.'; > >>>> >> if $input ~~ / (\d+) \s+ (\w+) / { > >>>> >> say $0.^name; # Match > >>>> >> say $0; # ｢9｣ > >>>> >> say $1.^name; # Match > >>>> >> say $1; # ｢million｣ > >>>> >> say $/; > >>>> >> # ｢9 million｣ > >>>> >> # 0 => ｢9｣ > >>>> >> # 1 => ｢million｣ > >>>> >> } > >>>> >> } > >>>> >> > >>>> >> say '---'; > >>>> >> > >>>> >> { # Moving the pattern to var which we interpolate into match > >>>> >> my $input = 'There are 9 million bicycles in beijing.'; > >>>> >> my $pattern = rx{ (\d+) \s+ (\w+) }; > >>>> >> if $input ~~ / <$pattern> / { > >>>> >> say $0.^name; # Nil > >>>> >> say $0; # Nil > >>>> >> say $1.^name; # Nil > >>>> >> say $1; # Nil > >>>> >> say $/; # ｢9 million｣ > >>>> >> } > >>>> >> } > >>>> >> > >>>> >> In the second case, the match clearly works, but it behaves as > >>>> >> though the capture groups aren't there. > >>>> >> > >>>> >> > >>>> >> raku --version > >>>> >> > >>>> >> Welcome to 𝐑𝐚𝐤𝐮𝐝𝐨™ v2020.10. > >>>> >> Implementing the 𝐑𝐚𝐤𝐮™ programming language v6.d. > >>>> >> > >>>> >
