testing if divisible by?
Paul
Thanks.
Philip Potter
> Hello all. How can I test to see if a number is divisible by say, 40?
> Thanks.
Use the modulo operator %. Given integers $x and $y, the expression $x
% $y gives the remainder when $x is divided by $y. As a result, if
(and only if) $x is exactly divisible by $y, $x % $y is equal to 0.
#!perl
use 5.010; # for 'say'
say 5 % 2;
say 6 % 2;
say 7 % 2;
say 79 % 40;
say 80 % 40;
say 81 % 40;
For more information, see
http://perldoc.perl.org/perlop.html#Multiplicative-Operators
Phil
Shawn H Corey
> Hello all. How can I test to see if a number is divisible by say, 40?
> Thanks.
>
>
See `perldoc perlop` and search for /Multiplicative Operators/ Read the
part about the % operator.
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Shawn
Programming is as much about organization and communication
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I like Perl; it's the only language where you can bless your
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Jamie L. Penman-Smithson
> Hello all. How can I test to see if a number is divisible by say, 40?
Use the modulo operator:
my $a = 40;
my $b = 1;
if ($a % $b == 0) {
print "$b is divisible by $a\n";
}
-j
Uri Guttman
JLP> On Sat, 2010-05-01 at 07:15 -0400, Paul wrote:
>> Hello all. How can I test to see if a number is divisible by say, 40?
JLP> Use the modulo operator:
JLP> my $a = 40;
JLP> my $b = 1;
JLP> if ($a % $b == 0) {
no need for the == 0 if you invert the test with unless or change the
print text.
JLP> print "$b is divisible by $a\n";
JLP> }
uri
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Jay Savage
> On 1 May 2010 12:15, Paul <opens...@unixoses.com> wrote:
>> Hello all. How can I test to see if a number is divisible by say, 40?
>> Thanks.
>
> Use the modulo operator %. Given integers $x and $y, the expression $x
> % $y gives the remainder when $x is divided by $y. As a result, if
> (and only if) $x is exactly divisible by $y, $x % $y is equal to 0.
>
And there's the rub: "number" ne "integer".
% is fine if you're only interested in integers, but if you want to
compare other numbers use fmod() from POSIX.pm:
perl -MPOSIX -wle 'print POSIX::fmod(35, 17.5)'
It's considerably slower than %, but it gets the job done.
HTH,
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Philip Potter
> On Sat, May 1, 2010 at 7:45 AM, Philip Potter <philip....@gmail.com> wrote:
>> On 1 May 2010 12:15, Paul <opens...@unixoses.com> wrote:
>>> Hello all. How can I test to see if a number is divisible by say, 40?
>>
>
>
> % is fine if you're only interested in integers, but if you want to
> compare other numbers use fmod() from POSIX.pm:
>
> perl -MPOSIX -wle 'print POSIX::fmod(35, 17.5)'
fmod is a fine replacement for % in general for testing remainders of
floating-point valued quotients, but using it as a divisibility test
requires caution and serious consideration of a different approach. It
has the same issues as a floating-point equality test: that is,
because floating-point is an inexact representation, the results can
depend on whether a value was rounded up or down:
D:\>perl -MPOSIX -wle "print POSIX::fmod(0.2, 0.1)"
0
D:\>perl -MPOSIX -wle "print POSIX::fmod(0.3, 0.1)"
0.1
D:\>perl -MPOSIX -wle "print POSIX::fmod(0.4, 0.1)"
0
D:\>perl -MPOSIX -wle "print POSIX::fmod(0.5, 0.1)"
0.1
These examples have strange results because 0.1 is not exactly
representable in binary floating-point.
Phil