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functional programming: sort to shuffle

by stefp (Vicar)
on Sep 03, 2001 at 13:24 UTC ( #109836=obfuscated: print w/replies, xml ) Need Help??

It shuffles the parameters list:
sub shuffle { map { @_=sort { int (3*rand)-1 } @_ } 0..5 }
Note that I go thru 6 iterations to get "sufficient" disorder.

see Why I like functional programming by tilly.

-- stefp

Replies are listed 'Best First'.
Re: sort to shuffle
by demerphq (Chancellor) on Sep 03, 2001 at 15:06 UTC
    Cool idea. stefp++.
    Curious if sort could get into a 'never finish' scenario if the right values came up from rand though?
    Thought you might like this version of the fisher yates shuffle.
    sub fy_shuf{my($l,$c,$r)=@_;map{$r=int(rand($_+1)); @$l[$_,$r]=@$l[$r,$_]}reverse 0..$#$l for 0..$c||0}; my @a=(1..52); fy_shuf(\@a,5);
    UPDATE
    Having had a look at japhy home node I borrowed an idea from him and reduced it more. (Oh and I decided that shuffling mutiple times was unecessary.)
    sub fy_shuf{my($l,$r)=@_;map{$r=int(rand(@$l-$_+1));@$l[-$_,$r]=@$l[$r +,-$_]}0..$#$l};

    Yves
    --
    You are not ready to use symrefs unless you already know why they are bad. -- tadmc (CLPM)

      It really depends on the internal sort algorithm. The "never finish" scenario is not the worse possible one: on some old versions of perl, my shuffle function crashes the perl interpretor :)

      That is why this really belongs to the obfuscation category... to answer a remark on the CB.

      Anyway, on 5.6, it works fine and dandy.

      -- stefp

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