Here is your code with some comments on errors, etc.

I have added some debug prints so you can see what gives. This is alway a good start to debugging.

First you are not opening the file "correctly" with a path and an I/O operator like < for read and > or >> for write.

The uninitialised values arise because you increment $foo to a value one past the last element. In the exapmle the while fails after the first iteration. We have an array of length 1 ie only element '0' but $foo = 1. You use this value as a count of the number of elements and iterate from 0..1, thus using an uninit value.

I could not resist cleaning up your code. See the final version. Of all the changes the split/\s+/,$line is one of the more important as now your data file can be "dirty" with multiple spaces between values and still work. Single space delimiters are fine provided no human hands ever touch the data file!

hope this helps

tachyon

#!/usr/bin/perl -w

$foo = 0;

# not a good way to open a file, 
# should be open FOO, "<$path/$file"
# also print after die not needed
open (VECTORS, "vectors") or die print "Cannot open 'vectors' file: $!
+\n";

while ($line = <VECTORS>) {
    if ($line =~ /\d/) {
        chomp $line;
        ($vectorA[$foo], $angleA[$foo], $vectorB[$foo], $angleB[$foo])
+ = split " ", $line, 4;
        
        # debugging print
        print"file input $foo: $vectorA[$foo], $angleA[$foo], $vectorB
+[$foo], $angleB[$foo]\n";
        
        ++$foo;
    }
}

# this is wrong $foo is 1 as you incremented it
# at the end of the loop, so when you hit the last
# element you increment $foo 1 too much and set
# $max_vector to 1 to0 much
$max_vectors = $foo;

# debugging print
print "\$max_vectors: $max_vectors\n";

for ($foo = 0; $foo <= $max_vectors; ++$foo) {
 
    # debugging print
    print"\$foo $foo\n";

    # this should be = for first assignment not +=
    $X[$foo] += ($vectorA[$foo] * cos($angleA[$foo]));
    $X[$foo] += ($vectorB[$foo] * cos($angleB[$foo]));
}

# this is another loop just like the one above
# why not put the two statements here with the two above?
# and just have the one loop
# this is also the longhand++ loop syntax
for ($foo = 0; $foo <= $max_vectors; ++$foo) {

    # debugging print
    print"\$foo $foo\n";
 
    # this should be = for first assignment not +=
    $Y[$foo] += ($vectorA[$foo] * sin($angleA[$foo]));
    $Y[$foo] += ($vectorB[$foo] * sin($angleB[$foo]));
}

# Must do more stuff here, ie. finish and convert to degrees after sin
+() and cos()

foreach $X (@X) {
    print "$X\n";
}

print "\nblah\n\n";

foreach $Y (@Y) {
    print "$Y\n";
}

#!/usr/bin/perl -w

use strict;
my (@vectorA, @angleA, @vectorB, @angleB, @X, @Y);

open (VECTORS, "<c:/vectors.txt") or die "Oops $!\n";

my $i = -1;
while (my $line = <VECTORS>) {
    next unless $line =~ /\d/;
    $i++;
    ($vectorA[$i], $angleA[$i], $vectorB[$i], $angleB[$i]) = split/\s+
+/,$line;
}
die "Sorry, no data!\n" if $i == -1;
my $max_vectors = $i;

for (0..$max_vectors) {
    $X[$_] = ($vectorA[$_] * cos($angleA[$_]));
    $X[$_] += ($vectorB[$_] * cos($angleB[$_]));
    $Y[$_] = ($vectorA[$_] * sin($angleA[$_]));
    $Y[$_] += ($vectorB[$_] * sin($angleB[$_]));
}

# Must do more stuff here, ie. finish and convert to degrees after sin
+() and cos()

print "$_\n" for @X;

print "\nblah\n\n";

print "$_\n" for @Y;
[download]

# Initialize the variables that are causing problems
$vectorA[1] = 0;
$angleA[1] = 0;
$vectorB[1] = 0;
$angleB[1] = 0;
[download]

open (VECTORS, "vectors") or die print "Cannot open 'vectors' file: $!
+ \n";
[download]

Simply type perl -d myprogram.pl to debug the perl script myprogram.pl. You can move from one line of your main program to the next by hitting the 'n' key. For more info type 'perldoc perldebtut' from the command line.

For a long time I avoided using debug mode, but now I know that it is my friend.

C-.

When I run my script, I get this as output:

Use of uninitialized value in cos at ./vectors.pl line 19, <VECTORS> l
+ine 4.
Use of uninitialized value in multiplication (*) at ./vectors.pl line 
+19, <VECTORS> line 4.
Use of uninitialized value in cos at ./vectors.pl line 20, <VECTORS> l
+ine 4.
Use of uninitialized value in multiplication (*) at ./vectors.pl line 
+20, <VECTORS> line 4.
Use of uninitialized value in sin at ./vectors.pl line 24, <VECTORS> l
+ine 4.
Use of uninitialized value in multiplication (*) at ./vectors.pl line 
+24, <VECTORS> line 4.
Use of uninitialized value in sin at ./vectors.pl line 25, <VECTORS> l
+ine 4.
Use of uninitialized value in multiplication (*) at ./vectors.pl line 
+25, <VECTORS> line 4.
6.25584093881723
0
10.2844455635215
0
[download]

If I leave out the '-w' option, the nasty messages go away but the useless zeros after meaningful input don't. I'll have to take a look at those in the morning.

You should never simply take out -w or use strict; to get rid of an error or warning. by doing so, you haven't really gotten rid of the error, you've simply suppressed the message saying that there is such an error. Doing this is just asking for more errors and instability to crop up without you knowing it.

- Sherlock

Skepticism is the source of knowledge as much as knowledge is the source of skepticism.