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Eliminating Trailing Zeros

by Anonymous Monk
on Jul 17, 2003 at 14:22 UTC ( #275219=perlquestion: print w/replies, xml ) Need Help??

Anonymous Monk has asked for the wisdom of the Perl Monks concerning the following question:

I want to format a real number to 2.4f format. This is simple one would say just use $n=sprintf("%2.4f",$n); , where $n is the number to be rounded. However when I do this I get a number like 23.4600 or 23.0000, which is indeed %2.4f format but I want to eliminate the trailing zeros and decimal where needed resulting in 23.46 and 23

This is a chunk of the code that does it:

$n=sprintf("%2.4f",$n); $n =~ s/0+$//; $n =~ s/\.$//;

This does work just fine, however I would like to find away to do the substitution by combining the these 2 separate substitutions into 1 more eloquant one (single line).... or perhaps an even better way to do it all together. Thank you for your help.

Replies are listed 'Best First'.
Re: Eliminating Trailing Zeros
by jmcnamara (Monsignor) on Jul 17, 2003 at 15:18 UTC

    Use the g format instead of f and no further formatting should be required:
    $ perl -e 'printf "%2.4g\n", 23.05' 23.05 $ perl -e 'printf "%2.4g\n", 23.00' 23
    See the sprintf manpage for more details:
    g The double argument is converted in style f or e (or E for G conversions). ... Trailing zeros are removed from the fractional part of the result; ...


Re: Eliminating Trailing Zeros
by dreadpiratepeter (Priest) on Jul 17, 2003 at 14:29 UTC
    $n =~ s/\.0*$|0*$//;
    UPDATE: fixed lack of reading requirements

    "Worry is like a rocking chair. It gives you something to do, but it doesn't get you anywhere."
      That's broken. It deletes the period but leaves in the trailing zeros. This is better, and does what's requested:

      Gary Blackburn
      Trained Killer

      A reply falls below the community's threshold of quality. You may see it by logging in.
      That is Perfect! Thanks!
Re: Eliminating Trailing Zeros
by Aristotle (Chancellor) on Jul 17, 2003 at 15:15 UTC
    For completeness' sake, one that doesn't break when there's no decimal point.

    Makeshifts last the longest.

Re: Eliminating Trailing Zeros
by ihb (Deacon) on Jul 17, 2003 at 20:16 UTC
        $n += 0;


      I can't believe we were all stuck in string mode when the answer was that obvious.

      Makeshifts last the longest.

Re: Eliminating Trailing Zeros
by Lachesis (Friar) on Jul 17, 2003 at 14:36 UTC
    $n =~ s/\.?0+$//;
    Update: Thanks to dreadpiratepeter for spotting my stupid mistake.
    The better option would be $n =~ s/\.\d*?0+$//;
    That worked with my test data but only because I wasn't using formatted strings so trailing 0s were already dealt with. Doh!
    With a %x.yf formatted string the original approach will work fine.
    jmcnamara came up with probably the best solution Re: Eliminating Trailing Zeros
      works except for:
      it doesn't work if you have this:
      (the sprintf before it:

      $n=sprintf("%2.4f",$n); $n =~ s/\.\d*?0+$//;

      What do you think? Is there one that will cover this scenario too?

        Use a sexeger (a reverse regex):
        $n = reverse scalar sprintf("%2.4f",$n); $n =~ s/^0+//g; $n = reverse scalar $n; $n =~ s/\.$//g;
        now if could just condense those two regexes into one ... but sometimes, brute force is better than cleverness.

        UPDATE: aha!

        $n = reverse scalar sprintf("%2.4f",$n); $n =~ s/^0+\.?//g; $n = reverse scalar $n;
        that was easier than i thought ... unless i missed something [And i did ... glad i retested, because i had forgotten to espace the dot .. bad jeffa. Also, the scalar keywords are not necessary].

        And jmcnamara++ ... that's the best solution posted (IMHO) since you already are using sprintf.


        (the triplet paradiddle with high-hat)
      That turns 420000 into 42

      "Worry is like a rocking chair. It gives you something to do, but it doesn't get you anywhere."
Re: Eliminating Trailing Zeros
by demerphq (Chancellor) on Jul 17, 2003 at 15:04 UTC
    ($n=sprintf "%2.4f",$n)=~s/\.?0+$//;


    <Elian> And I do take a kind of perverse pleasure in having an OO assembly language...
Re: Eliminating Trailing Zeros
by RollyGuy (Chaplain) on Jul 17, 2003 at 14:40 UTC
    $n =~ s/\.?0*$//;

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