in reply to Choose random element of array?

Or, if you want "pick once" functionality (consumes the original array): 
my $color = splice(@colors, rand @colors, 1);

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Cheers,
Matt

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Re: Re: Choose random element of array?
by hsinclai (Deacon) on May 28, 2004 at 16:50 UTC
    As mojotoad points out, when you need that "pick once" functionality from the array, splice() works wonders.. (in the example below, the @testarray has 1052 elements, so the counter runs out at 1051:) 

    use strict;

my $counter = 0;
my $randstring;
my @testarray = ( 'a' .. 'z', 'A' .. 'Z', '0' .. '999' );

do { $randstring .= splice(@testarray, int rand @testarray, 1); 
     ++$counter;
} until $counter == 1051;

print "$randstring\n";

    [download]


[reply]
[d/l]
      Nice snippet. I couldn't help but point out that you already have a built-in counter -- the number of elements in the array. Reworking your example a bit, we get the following: 
      use strict;                

my $randstring;
my @testarray = ( 'a' .. 'z', 'A' .. 'Z', '0' .. '999' );

$randstring .= splice(@testarray, rand @testarray, 1)
  while @testarray;

print "$randstring\n";

      [download]
      Cheers,
      Matt
[reply]
[d/l]

        That's definitely better -thanks!

[reply]

      What you have there is essentially a shuffle and join. Using splice to shuffle is tempting, but inefficient. perlfaq4 already covers this topic well, and List::Util's shuffle makes it convenient.

[reply]
        Thanks for these pointers, it will take me to the next level of understanding this stuff..

        Now, at what point, do you do the Fisher-Yates thing in your code.. when you've got a larger array to deal with I guess - but how large?

        Tried looking to see if List::Util uses a Fisher-Yates but it seems to be a .so binary, a library.

        You do realize, that now, I will not ever be able to type the word "splice" without severe pangs of guilt and inefficiency...

[reply]

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