FAQ: How do I get a random number between X and Y?

From: PerlFAQ Server (comdog_at_panix.com)
Date: 10/20/04


Date: Wed, 20 Oct 2004 10:10:16 +0000 (UTC)

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4.11: How do I get a random number between X and Y?

    "rand($x)" returns a number such that "0 <= rand($x) < $x". Thus what
    you want to have perl figure out is a random number in the range from 0
    to the difference between your *X* and *Y*.

    That is, to get a number between 10 and 15, inclusive, you want a random
    number between 0 and 5 that you can then add to 10.

        my $number = 10 + int rand( 15-10+1 );

    Hence you derive the following simple function to abstract that. It
    selects a random integer between the two given integers (inclusive), For
    example: "random_int_in(50,120)".

       sub random_int_in ($$) {
         my($min, $max) = @_;
          # Assumes that the two arguments are integers themselves!
         return $min if $min == $max;
         ($min, $max) = ($max, $min) if $min > $max;
         return $min + int rand(1 + $max - $min);
       }

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