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scuzzman

Dec 23rd, 2005 5:29 AM

A simple script isn't working correctly

I'm having trouble getting a very simple script to run and cannot figure out the problem. The script is as follows:

#!/usr/bin/perl -w



$level = 1;

$prod = (20 * $level) * (1.1 ** $level);



print "What is the amount of energy you\'re trying to accumulate? ";

chomp ( $goal = <STDIN> );



while ($prod <= $goal) {

  # print "$level\n"; # DEBUG: print the current level

  $level++;

}



print "\nRequired level for $goal energy from a solar planet is $level\n";

The problem is that the $prod never changes from 22 (which is what it evaluates to when $level = 1). Because $prod is based on the value of $level, shouldn't $prod change when $level does?

Arevos

Dec 23rd, 2005 5:43 AM

Quote:

Originally Posted by scuzzman

Because $prod is based on the value of $level, shouldn't $prod change when $level does?

No. And this is common in computer languages. The code:

$a = 2;

$b = 3;

$c = $a + $b;

Adds together the value of $a and $b, and puts the resulting number in $c. This value is static, because it's just a number.

In order to change the value, you need to perform the calculation again:

$b = 4;

$c = $a + $b;

scuzzman

Dec 23rd, 2005 5:57 AM

Thanks! Would changing this to a constant achieve my desired result, or would I need to just write a subfunction to repeatedly do the calculation?

Arevos

Dec 23rd, 2005 6:42 AM

Quote:

Originally Posted by scuzzman

Thanks! Would changing this to a constant achieve my desired result, or would I need to just write a subfunction to repeatedly do the calculation?

A subroutine sounds your best bet:

sub findProd {

    my $level = shift @_;

    return (20 * $level) * (1.1 ** $level);

}



...



$level++ while (findProd($level) <= $goal);

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