Programming Forums > Script Programming > Perl

scuzzman · Dec 23rd, 2005, 5:29 AM

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:

(Toggle Plain Text)

$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:

(Toggle Plain Text)

$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:

(Toggle Plain Text)

sub findProd {
    my $level = shift @_;
    return (20 * $level) * (1.1 ** $level);
}

...

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

Dec 23rd, 2005, 5:29 AM	#1
scuzzman Newbie Join Date: Dec 2005 Posts: 2 Rep Power: 0	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: (Toggle Plain Text) #!/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"; #!/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?

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Dec 23rd, 2005, 5:57 AM	#3
scuzzman Newbie Join Date: Dec 2005 Posts: 2 Rep Power: 0	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?

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Programming Forums > Script Programming > Perl

A simple script isn't working correctly