Looping variables - perl

Question

I'm working with perl to make a script that will work with Dot products/assorted vector math. I've got a working script ( Still very much in progress/needs refinement ) that will do what I ask.
#!/usr/bin/perl
use strict;
use warnings;
use diagnostics;
use Math::Vector::Real;
use 5.010;
use Math::Trig;
my $source = "./IN";
my $out = "./OUT";
open(IN, '<', $source) or die "Couldn't open $source: $!\n";
open(OUT, '>', $out) or die "Couldn't open $out: $!\n";
my(#data);
while (<IN>) {
push #data, [ split ];
}
my $v;
my $u;
$v = V(0, 0, 0);
$u = V(0, 0, 0);
my $i = 0;
sub maths {
my $dot = $v * $u;
my $mag1 = (sqrt ((#$v[0])**2 + (#$v[1])**2 + (#$v[2])**2 ));
my $mag2 = (sqrt ((#$u[0])**2 + (#$u[1])**2 + (#$u[2])**2 ));
my $prefinal = acos( ( $dot ) / ( $mag1 * $mag2 ) );
my $degrees = ( ( 180 / 3.14159 ) * ( $prefinal ) );
return ($degrees);
}
my $ref1 = $data[$i][0];
my $ref2 = $data[$i][1];
my $ref3 = $data[$i][2];
my $ref4 = $data[$i+1][0];
my $ref5 = $data[$i+1][1];
my $ref6 = $data[$i+1][2];
$v->[0] = $ref1;
$v->[1] = $ref2;
$v->[2] = $ref3;
$u->[0] = $ref4;
$u->[1] = $ref5;
$u->[2] = $ref6;
my $result = maths;
print "$result\n";
A lot of stuff in the script is vestigial and for ease to follow (For me).
What I desire it to do, is to have the script rotate through each line of the input file and perform the calculations on it.
Something akin to having :
foreach $i (#data) {
my $ref1 = $data[$i][0];
my $ref2 = $data[$i][1];
my $ref3 = $data[$i][2];
my $ref4 = $data[$i+1][0];
my $ref5 = $data[$i+1][1];
my $ref6 = $data[$i+1][2];
$v->[0] = $ref1;
$v->[1] = $ref2;
$v->[2] = $ref3;
$u->[0] = $ref4;
$u->[1] = $ref5;
$u->[2] = $ref6;
my $result = maths;
print "$result\n";
}
Anything is appreciated.

Answer 1

As per my comment, most of the functionality of your program is provided by the Math::Vector::Real module that you're already using
It looks like you want the angle in degrees between successive pairs of 3D vectors in your file. This code creates vectors from each line in the file until there are two vectors in #pair, and then uses atan2 to calculate the angle between them. DEG_PER_RAD is precalculated as a constant from the value of atan2(1,1) which is π ÷ 4 by definition
#!/usr/bin/perl
use strict;
use warnings;
use Math::Vector::Real;
use constant DEG_PER_RAD => 45 / atan2(1, 1);
my ( $source, $out ) = qw/ IN OUT /;
open my $in_fh, '<', $source or die qq{Unable to open "$source" for input: $!\n};
open my $out_fh, '<', $out or die qq{Unable to open "$out" for output: $!\n};
select $out_fh;
my #pair;
while ( <$in_fh> ) {
push #pair, V(split);
if ( #pair == 2 ) {
my $degrees = atan2(#pair) * DEG_PER_RAD;
print "$degrees\n";
shift #pair;
}
}
Update
To do the calculation for every possible pair of vectors, it is simplest to read the whole of the file into an array of vectors and process them from there with two nested loops
This code demonstrates. Insert it after the select call in the original program. It labels each line of output with the two array indices that gave rise to the angle
my #data;
push #data, V(split) while <$in_fh>;
for my $i ( 0 .. $#data-1 ) {
for my $j ( $i+1 .. $#data ) {
my $degrees = atan2(#data[$i,$j]) * DEG_PER_RAD;
print "[$i,$j] $degrees\n";
}
}

Answer 2

You could use the following:
my $v = V( #{ $data[$i+0] } );
my $u = V( #{ $data[$i+1] } );
Cleaned up:
#!/usr/bin/perl
use strict;
use warnings;
use Math::Trig qw( acos );
use Math::Vector::Real qw( V );
sub maths {
my ($v, $u) = #_;
my $dot = $v * $u;
my $mag1 = sqrt( $v->[0]**2 + $v->[1]**2 + $v->[2]**2 );
my $mag2 = sqrt( $u->[0]**2 + $u->[1]**2 + $u->[2]**2 );
my $prefinal = acos( $dot / ( $mag1 * $mag2 ) );
my $degrees = ( 180 / 3.14159 ) * $prefinal;
return $degrees;
}
{
my #data = map { V( split ) } <>;
for my $i (0..$#data-1) {
for my $j ($i+1..$#data) {
my $maths = maths(#data[$i, $j]);
print("$i,$j: $maths\n");
}
}
}
Or with Borodin's alternate method:
#!/usr/bin/perl
use strict;
use warnings;
use Math::Trig qw( acos atan2 );
use Math::Vector::Real qw( V );
use constant DEG_PER_RAD => 45 / atan2(1, 1);
{
my #data = map { V( split ) } <>;
for my $i (0..$#data-1) {
for my $j ($i+1..$#data) {
my $maths = atan2(#data[$i, $j]) * DEG_PER_RAD;
print("$i,$j: $maths\n");
}
}
}
Usage:
perl script.pl ./IN >./OUT