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Re^2: removing the white spaces

by japhy (Canon)
on Apr 13, 2006 at 13:31 UTC ( #543077=note: print w/ replies, xml ) Need Help??


in reply to Re: removing the white spaces
in thread removing the white spaces

RESIST THE URGE! Seriously, don't do that. It slows the whole thing down like you wouldn't believe.


Jeff japhy Pinyan, P.L., P.M., P.O.D, X.S.: Perl, regex, and perl hacker
How can we ever be the sold short or the cheated, we who for every service have long ago been overpaid? ~~ Meister Eckhart


Comment on Re^2: removing the white spaces
Re^3: removing the white spaces
by Tanalis (Curate) on Apr 13, 2006 at 14:00 UTC
      I've mentioned this before, I'll explain it again.

      The substitution s/^\s+// is simple and direct: replace a chunk of whitespace at the beginning of the string with nothing. The substitution s/\s+$// is simple and almost as direct: replace a chunk of whitespace followed by the end of the string with nothin. Sadly, it's not as "perfect" as the first one -- it matches each chunk of whitespace and examines it to see if it's at the end of the string or not. Oh well.

      When you say s/^\s+|\s+$//g, perl's regex engine gets stupid. Real dumb. It tries BOTH branches of that regex at every location in the string. EVERY LOCATION! EVEN WHERE THERE AREN'T SPACES! See for yourself with perl -mre=debug -e '$_ = " a  b   c    "; s/^\s+|\s+$//g' It's upsetting!

      So do it with two regexes. Give peace a chance.


      Jeff japhy Pinyan, P.L., P.M., P.O.D, X.S.: Perl, regex, and perl hacker
      How can we ever be the sold short or the cheated, we who for every service have long ago been overpaid? ~~ Meister Eckhart
Re^3: removing the white spaces
by codeacrobat (Chaplain) on Apr 13, 2006 at 14:20 UTC
    A noncapturing solution should speed things.
    untested:
    s/(?:^\s+)|(?:\s+$)//g
      First, the (?:...)'s aren't needed. Second, that's still no good.

      Jeff japhy Pinyan, P.L., P.M., P.O.D, X.S.: Perl, regex, and perl hacker
      How can we ever be the sold short or the cheated, we who for every service have long ago been overpaid? ~~ Meister Eckhart

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