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greatest common factor

by MrNobo1024 (Hermit)
on Feb 07, 2001 at 10:42 UTC ( #56906=snippet: print w/ replies, xml ) Need Help??

Description: These functions determine the greatest common factor or least common multiple of a set of numbers. gcf() and lcm() take two numbers as arguments, and multigcf() and multilcm() will take any amount. EDIT: fixed a bug in multigcf().
sub gcf {
  my ($x, $y) = @_;
  ($x, $y) = ($y, $x % $y) while $y;
  return $x;

sub lcm {
  return($_[0] * $_[1] / gcf($_[0], $_[1]));

sub multigcf {
  my $x = shift;
  $x = gcf($x, shift) while @_;
  return $x;

sub multilcm {
  my $x = shift;
  $x = lcm($x, shift) while @_;
  return $x;
Comment on greatest common factor
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Re: greatest common factor
by zeno (Friar) on Feb 07, 2001 at 16:16 UTC

    Very elegantly done. BTW, there's a typo in the sub multigcf: gcd should be gcf! Otherwise, a very nice offering.

    sub multigcf { my $x = shift; $x = gcd($x, shift) while @_; #should be gcf! return $x; }
Re: greatest common factor
by TheAmigo (Initiate) on Apr 16, 2015 at 19:51 UTC
    I found this function and it seemed reasonable, but some of my users reported that I was somtimes returning the wrong sign. Turns out that the function above has inconsistent behavior on negative numbers:

    gcf(-5, 5) = 5 gcf(5, -5) = -5

    when they should really both be 5.

    14 years late, but here's a fix. I changed my code so that gcf() ends with

    return abs $x;

Re: greatest common factor
by Anonymous Monk on Jun 12, 2014 at 08:03 UTC

    the copy/paste i needed

    many thanks ^_^

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