diff options
Diffstat (limited to 'gnu/usr.bin/perl/pod/perlfaq4.pod')
| -rw-r--r-- | gnu/usr.bin/perl/pod/perlfaq4.pod | 36 |
1 files changed, 17 insertions, 19 deletions
diff --git a/gnu/usr.bin/perl/pod/perlfaq4.pod b/gnu/usr.bin/perl/pod/perlfaq4.pod index 61503b6c57b..2ff7c7110ef 100644 --- a/gnu/usr.bin/perl/pod/perlfaq4.pod +++ b/gnu/usr.bin/perl/pod/perlfaq4.pod @@ -1,6 +1,6 @@ =head1 NAME -perlfaq4 - Data Manipulation ($Revision: 1.52 $, $Date: 2003/10/02 04:44:33 $) +perlfaq4 - Data Manipulation ($Revision: 1.6 $, $Date: 2003/12/03 03:02:44 $) =head1 DESCRIPTION @@ -362,9 +362,20 @@ pseudorandom generator than comes with your operating system, look at =head2 How do I get a random number between X and Y? -Use the following simple function. It selects a random integer between -(and possibly including!) the two given integers, e.g., -C<random_int_in(50,120)> +C<rand($x)> returns a number such that +C<< 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 I<X> and I<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: C<random_int_in(50,120)>. sub random_int_in ($$) { my($min, $max) = @_; @@ -415,14 +426,6 @@ Use the following simple functions: return 1+int((((localtime(shift || time))[5] + 1899))/1000); } -You can also use the POSIX strftime() function which may be a bit -slower but is easier to read and maintain. - - use POSIX qw/strftime/; - - my $week_of_the_year = strftime "%W", localtime; - my $day_of_the_year = strftime "%j", localtime; - On some systems, the POSIX module's strftime() function has been extended in a non-standard way to use a C<%C> format, which they sometimes claim is the "century". It isn't, @@ -1489,16 +1492,11 @@ the hash is to be modified. Use the rand() function (see L<perlfunc/rand>): - # at the top of the program: - srand; # not needed for 5.004 and later - - # then later on $index = rand @array; $element = $array[$index]; -Make sure you I<only call srand once per program, if then>. -If you are calling it more than once (such as before each -call to rand), you're almost certainly doing something wrong. +Or, simply: + my $element = $array[ rand @array ]; =head2 How do I permute N elements of a list? |