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Re: list of four digit lock combinations without repeated digits

by tybalt89 (Parson)
on Jun 20, 2018 at 20:18 UTC ( #1217052=note: print w/replies, xml ) Need Help??

in reply to list of four digit lock combinations without repeated digits

#!/usr/bin/perl # use strict; use warnings; (1 x 10) =~ /.+?(.).*?(.).*?(.)(?{print @-, "\n"})(*FAIL)/;

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Re^2: list of four digit lock combinations without repeated digits
by Lotus1 (Priest) on Jun 22, 2018 at 14:44 UTC

    I did ask for interesting solutions. It's going to take me a while to understand how this works. I found in perlvar a description of @- as being an array of the indexes of the matches. Thanks for posting.

    @- $-[0] is the offset of the start of the last successful match. $-[n] i +s the offset of the start of the substring matched by n-th subpattern +, or undef if the subpattern did not match. Thus, after a match against $_ , $& coincides with substr $_, $-[0], $ ++[0] - $-[0] . Similarly, $n coincides with substr $_, $-[n], $+[n] - + $-[n] if $-[n] is defined, and $+ coincides with substr $_, $-[$#-], + $+[$#-] - $-[$#-] . One can use $#- to find the last matched subgrou +p in the last successful match. Contrast with $#+ , the number of sub +groups in the regular expression. Compare with @+ . This array holds the offsets of the beginnings of the last successful +submatches in the currently active dynamic scope. $-[0] is the offset + into the string of the beginning of the entire match. The nth elemen +t of this array holds the offset of the nth submatch, so $-[1] is the + offset where $1 begins, $-[2] the offset where $2 begins, and so on.

      Here's another version without the @-

      Just match any four of the digits (from an ordered string).

      #!/usr/bin/perl # use strict; use warnings; '0123456789' =~ /(.).*?(.).*?(.).*?(.)(?{print "$1$2$3$4\n"})(*FAIL)/;

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