random negative toggle function

zentara has asked for the wisdom of the Perl Monks concerning the following question:

UPDATE: Sorry, I didn't word my original question clearly, I was looking for a function to return 1 or -1 randomly. My code below returns an even 50-50 distribution. I was looking for an even distribution, but random at any one time.

Hi, I recently had a need to run an loop and each time thru the loop I needed to alternatively add or subtract a variable. So I came up with:

#!/usr/bin/perl

@hits = (-1,1);

for(1..10){
print toggle(),"\n";
}

sub toggle{
push (@hits,shift(@hits));
return $hits[0];
}
[download]

I have a feeling that there is some "golfed way" of doing this in a more simple fashion. I thought about taking the output of rand, and make the number 1 if > .5 and -1 if less than .5. Anyone have ideas? Thanks.

Comment on random negative toggle function Download Code

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Re: random negative toggle function by !1 (Hermit) on Nov 15, 2003 at 19:37 UTC
As another way to do it: `perl -le'print +(-1,1)[rand 2]' # or as a sub sub toggle { (-1,1)[rand 2] }` [download] Of course, that's the short and simple way. I hope this helps you with your problem.	[reply] [d/l]
Re: random negative toggle function by Limbic~Region (Chancellor) on Nov 15, 2003 at 19:14 UTC
zentara, I am replying after you made your update: `#!/usr/bin/perl -w use strict; print toggle(), $/ for 1 .. 10; sub toggle { int rand 2 ? 1 : -1; }` [download] Cheers - L~R	[reply] [d/l]
Re: random negative toggle function by jeffa (Bishop) on Nov 15, 2003 at 21:26 UTC
How about Abigail-II's Tie::FlipFlop? `use Tie::FlipFlop; tie my $flipflop => Tie::FlipFlop => -1,1; print $flipflop for 1..10;` [download] These days, i like to search the CPAN before i add YAUM (yet another utility method) to my YAOASL (yet another obscure and specialized library). The CPAN has become my utility library. jeffa L-LL-L--L-LL-L--L-LL-L-- -R--R-RR-R--R-RR-R--R-RR B--B--B--B--B--B--B--B-- H---H---H---H---H---H--- (the triplet paradiddle with high-hat)	[reply] [d/l]
Re: negative toggle function by CombatSquirrel (Hermit) on Nov 15, 2003 at 18:06 UTC
How about this: `my $toggle = -1; for (1..10) { print $toggle *= -1, $/; }` [download] CombatSquirrel. Entropy is the tendency of everything going to hell.	[reply] [d/l]
Re: negative toggle function by EdwardG (Vicar) on Nov 15, 2003 at 18:43 UTC
For a solution perhaps more sophisticated that the classic negate-$x-each-iteration perhaps it would be illuminating to look at Easy binary toggle at fixed intervals, or perhaps Flipper, and of course, merlyn has probably written an article about this :) IMHO the simplest is: `d:\>perl -e "print +($a += 1) %= 2 for 1..10" 1010101010` [download]	[reply] [d/l]
Re: random negative toggle function by EdwardG (Vicar) on Nov 15, 2003 at 19:06 UTC
Random 1 or 0 is even easier `d:\>perl -e "print int rand()+.5 for 1..10" 1110110000` [download]	[reply] [d/l]
Re: random negative toggle function by zentara (Cardinal) on Nov 16, 2003 at 22:50 UTC
Thanks for the good answers. In case you were wondering, I was trying to simulate random motion, like deviation from a straight line trajectory. I needed the -1 instead of a 0 because it would plug directly into the motion equation.	[reply]