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perl loop problem (from a beginner)

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Join Date: Apr 2009

Posts: 7

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LSU_223

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perl loop problem (from a beginner)

May 7th, 2009

Hi - Major novice here. I'm trying to write a code that starts with a user defined number (lets say "N"), picks a random number between 1 and N (lets say "R"), pushes R onto an array, subtracts R from N, then picks the next random number from (N-R), pushes the new number onto the array...etc...and loops this until (N-R)==0.

The code I have seems to go into an infinite loop or something... any help would be great and if there's an obvious solution, I apologize in advance. Thanks!

use warnings; use strict;
my @list;
print "Enter number of OTUs:";
my $start = <STDIN>;
do {
my $rand = int(rand($start));
push (@list, $rand);
$start-=$rand;
} until ($start ==0);

print "@list";

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Join Date: Mar 2006

Posts: 898

Reputation: KevinADC has a spectacular aura about

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KevinADC

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Practically a Posting Shark

Re: perl loop problem (from a beginner)

May 7th, 2009

"do" is not really a loop but if you use "until" or "while" with it you can get it to act like a loop. The problem with your code is that $start never has a chance to equal zero so the "do" block just keeps getting repeated over and over. Thix will help you see whats going on:

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use warnings;
use strict;
my @list;
print "Enter number of OTUs:";
my $start = <STDIN>;
chomp $start;
do {
my $rand = int(rand($start));
print "rand = $rand\n";
push (@list, $rand);
$start-=$rand;
print "\$start = $start\n";
} until ($start == 0);
 
print "@list";
use warnings;
use strict;
my @list;
print "Enter number of OTUs:";
my $start = <STDIN>;
chomp $start;
do {
my $rand = int(rand($start));
print "rand = $rand\n";
push (@list, $rand);
$start-=$rand;
print "\$start = $start\n";
} until ($start == 0);

print "@list";