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Re: Flip-flop won't DWIM

by akho (Hermit)
on May 21, 2009 at 15:49 UTC ( #765484=note: print w/ replies, xml ) Need Help??


in reply to Flip-flop won't DWIM

The /./ matches E, so flip-flop starts over.


Comment on Re: Flip-flop won't DWIM
Re^2: Flip-flop won't DWIM
by akho (Hermit) on May 21, 2009 at 15:57 UTC
      Yes. However, List::MoreUtils is not in core, so it's not something I want to rely on in the current circumstance.
Re^2: Flip-flop won't DWIM
by wu-lee (Beadle) on May 21, 2009 at 15:58 UTC
    Right. Of course, silly me.

    Ok, so this does what I want:

    perl -lwe '$x = 1; print join " ", grep { scalar($x++../D/) } qw(A B C + D E F)' # prints: # A B C D
    Although this is not particularly neat. Is there a better way?
      Actually, that doesn't, but this does:
      perl -lwe '$x = 0; print join " ", grep { scalar(!$x++../D/) } qw(A B + C D E F)' # prints: # A B C D
      Your code prints "A B C D E F" for me, and I cannot see why it would print anything else.

      This seems to work if you insist on using flip-flop:

      $x = 1; print join " ", grep { $x..(($x=0) or /D/) } qw(A B C D E F);
      However, you could copy stuff from List::MoreUtils.
      The "++" does nothing.
Re^2: Flip-flop won't DWIM
by Roy Johnson (Monsignor) on May 21, 2009 at 20:30 UTC
    So use the match-once operator (no need for an actual pattern; the empty pattern works fine):
    print join ' ', grep scalar(??../D/), ('A'..'F');

    Caution: Contents may have been coded under pressure.
      Aha! Finally, a use for the match-once operator! And it seems to be tailor made for this problem. Bravo!

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