Hi Aureliano!
Others will certainly have a more informed answer, but I think it
might be because:
1). Set operations in general in Perl6 (on characters, etc.) may use a
unordered matching algorithm to enhance speed, and/or
2). I didn't explicitly call a "Sort" method, function or routine in
matching the characters, and/or
3). The resulting character order (probably represented internally as
Unicode codepoints), may indeed have some sort of order to them, but
that order/pseudo-order is either A. related to their initial position
in the input string (0,1,2,3...), or B. that order/pseudo-order is
related to each character's numeric representation in Unicode.
Below I convert the code to accept two integers instead of two
strings. I set up a few different "return" lines for you to check out.
You will see that the (second) "return" line that calls ".sort" as the
last method indeed returns a set of integers in numerical order! But
it also looks as though the (first) return line without an explicit
".sort" call ALSO returns the Intersection Set in numerical order,
"(set(0 2 4 6 8))".
my Int $u = 24680;
my @s = $u.comb.unique;
say @s ; # [2 4 6 8 0]
sub matching_chars(Int $a, Int $b) {
my @c = $a.comb.unique;
my @d = $b.comb.unique;
#return @c (&) @d; # Returns Intersection Set (Ints)
#return [@c (&) @d].sort; # Returns Sorted Set (Ints)
return [@c (&) @d].sort.Str; # Returns varying order (Strs)
}
say matching_chars(24680, 1234567890); # RETURNS (set(0 2 4 6 8))
So I think Perl6 may have fast integer matching/sorting algorithms
built-in, but the built-in matching/sorting algorithms for characters
may be somewhat different, different enough to require a
explicit/final (e.g. alphabetic) sort, if that's what the programmer
desires.
HTH, Bill.
On Sun, Sep 1, 2019 at 10:10 PM Aureliano Guedes
<guedes.aureli...@gmail.com> wrote:
>
> Why does it dont return ordered for neither of those lists?
> I mean:
>
> my $u = "24680";
> my @s = $u.comb.unique;
> say @s ; # [2 4 6 8 0]
>
> sub matching_chars(Str $a, Str $b) {
> my @c = $a.comb.unique;
> my @d = $b.comb.unique;
> return ~[@c (&) @d];
> }
>
> say matching_chars("24680", "1234567890"); # says 2 0 8 4
>
> On Mon, Sep 2, 2019 at 1:20 AM William Michels via perl6-users
> <perl6-us...@perl.org> wrote:
>>
>> Thanks Simon, good point. I ran into the same trouble as others trying
>> to get the answer via regex, and switched over to sets as an
>> alternative. I'll confess I completely missed that Yary's Perl5 code
>> returned the substring "8420" present in his test "19584203" string,
>> and that was the answer he was going for.
>>
>> Simon and Eirik, I still think there might be some value in calling
>> the .unique method on $chars.comb as in "$chars.comb.unique". But I
>> haven't had the opportunity to check code efficiency +/- the
>> ".unique" method call.
>>
>> For those interested in using Sets as a solution, you can stringifying
>> the 'return' line (below). Still working on using "join()" to
>> concatenate!
>>
>> sub matching_chars(Str $a, Str $b) {
>> my @c = $a.comb.unique;
>> my @d = $b.comb.unique;
>> #return (~[@c (&) @d]).^name;
>> return ~[@c (&) @d];
>> }
>>
>> say matching_chars("24680", "19584203"); # says 2 0 8 4
>> say matching_chars('+\/\]\[', 'Apple ][+//e'); # says [ + ] /
>> say matching_chars("Lorem ipsum dolor sit amet, consectetuer
>> adipiscing elit.", "abcdef"); # says c a d e
>>
>>
>> HTH, Bill.
>>
>> PS. Simon, thanks for all the great Youtube videos you've done from LondonPM!
>>
>> https://youtu.be/yt8SrZ_V_50
>> https://youtu.be/9M1xZQ0_Skw
>>
>>
>>
>>
>>
>>
>>
>>
>> On Sun, Sep 1, 2019 at 9:59 AM Simon Proctor <simon.proc...@gmail.com> wrote:
>> >
>> > Using a set would be good but it doesn't give you the matching string from
>> > the original (which is what I thought was required) otherwise Sets would
>> > be my first thought.
>> >
>> > On Sun, 1 Sep 2019, 17:57 William Michels, <w...@caa.columbia.edu> wrote:
>> >>
>> >> Hi Yary and Paul and Simon,
>> >>
>> >> I ran into the same difficulties as Yary with repeated characters, so
>> >> I tried the .unique method. Then after a while, I realized that
>> >> problems like this might best be treated as "Set" problems in Perl6.
>> >> Note the Set Intersection operator "(&)" below:
>> >>
>> >> sub matching_chars(Str $a, Str $b) {
>> >> my @c = $a.comb.unique;
>> >> my @d = $b.comb.unique;
>> >> #say @c; say @d;
>> >> return @c (&) @d;
>> >> }
>> >>
>> >> say matching_chars("24680", "19584203"); #RETURNS set(0 2 4 8)
>> >> say matching_chars('+\/\]\[', 'Apple ][+//e'); #RETURNS set(+ / [ ])
>> >>
>> >>
>> >> https://docs.perl6.org/routine/Set
>> >> https://docs.perl6.org/language/operators#infix_(&),_infix_∩
>> >>
>> >> HTH, Bill.
>> >>
>> >>
>> >> On Sat, Aug 31, 2019 at 8:59 PM Paul Procacci <pproca...@gmail.com> wrote:
>> >> >
>> >> > I'm not entirely sure if this is the correct answer, but if you define
>> >> > your own custom character class
>> >> > with a 'regex' object, you can use that in the grouping.
>> >> >
>> >> > sub matching_chars(Str $chars_to_match, Str $_) {
>> >> > my regex x { $chars_to_match ** 1 };
>> >> > m/<[<x>]>/;
>> >> > }
>> >> >
>> >> > The above worked for me in the very small testing I did.
>> >> >
>> >> > ~Paul
>> >> >
>> >> > On Sat, Aug 31, 2019 at 9:54 PM yary <not....@gmail.com> wrote:
>> >> >>
>> >> >> I found something easy in Perl 5 that's puzzling me in Perl 6-
>> >> >> specifying a character class via a variable.
>> >> >>
>> >> >> Perl 5:
>> >> >> sub matching_chars {
>> >> >> (my $chars_to_match, local $_) = @_;
>> >> >> /([$chars_to_match]+)/
>> >> >> }
>> >> >>
>> >> >> say matching_chars('24680', '19584203'); # says 8420
>> >> >> say matching_chars('+\/\]\[', 'Apple ][+//e'); # says ][+//
>> >> >>
>> >> >> Perl 6:
>> >> >> sub matching_chars(Str $chars_to_match, Str $_) {
>> >> >> # warnings, treats as string not variable
>> >> >> m/<[$chars_to_match]>/;
>> >> >> }
>> >> >>
>> >> >> How do I get Perl 6 to interpret a variable in the contents of a
>> >> >> character class?
>> >> >> From http://docs.perl6.org/language/regexes#Regex_interpolation I'd
>> >> >> think that Rakudo would use the literal contents of $chars_to_match,
>> >> >> instead it's using the literal chars "$ c h a r s _ t o _ m a t c h"
>> >> >> and warning about repeated c, underscore, etc.
>> >> >>
>> >> >> -y
>> >> >
>> >> >
>> >> >
>> >> > --
>> >> > __________________
>> >> >
>> >> > :(){ :|:& };:
>
>
>
> --
> Aureliano Guedes
> skype: aureliano.guedes
> contato: (11) 94292-6110
> whatsapp +5511942926110
