How to use variables in a equation using Perl - perl

Question

I'm trying to use possible variables in a equation with Perl.
For example:
#!/usr/bin/perl -w
$a = "yellow";
$b = "orange";
$c = "col1fl0ur";
$c = $a + $b;
print "$a + $b = $c \n";
I want to be able to state the value for each variable $a, $b, $c, then be able to say that
$a + $b = "col1fl0ur"
You may ask; whats the point? just print out col1fl0ur, butI want to be able to use many more variables as well, such as in this case:
#!/usr/bin/perl -w
###values###
$a = "yellow";
$b = "orange";
$c = "col1fl0ur";
$d = "derp";
$e = "oplo";
$f = "qwerty";
###defining the equation###
$c = $a + $b;
$d = $a + $c;
$f = $d + $c;
###Printing###
print "$a + $b = $c \n";
print "$a + $c = $d \n";
print "$d + $c = $f \n";

Answer 1

It would help a lot if you explained your real problem, but something like this may help.
Note that you should never use $a and $b in live code as they are reserved variable names.
use strict;
use warnings;
my ($a, $b, $c, $d, $e, $f) = qw( yellow orange col1fl0ur derp oplo qwerty );
### defining the equation ###
my %sum;
$sum{$a}{$b} = $c;
$sum{$a}{$c} = $d;
$sum{$d}{$c} = $f;
### Printing ###
for my $pair ([$a, $b], [$a, $c], [$d, $c]) {
my ($p1, $p2) = #$pair;
printf "%s + %s = %s\n", $p1, $p2, $sum{$p1}{$p2};
}
output
yellow + orange = col1fl0ur
yellow + col1fl0ur = derp
derp + col1fl0ur = qwerty
If you want $b + $a to be the same as $a + $b then you will have to say so explicitly. For example,
$sum{$a}{$b} = $c;
$sum{$b}{$a} = $c;

Answer 2

you may use Overload pragma..
You can create a new package as follows:
package Tst;
use overload "+" => \&myadd;
sub new {
my $class = shift;
my $value = shift;
return bless \$value => $class;
}
sub myadd {
my ($x, $y) = #_;
$x = ref($x) ? $$x : $x;
$y = ref($y) ? $$y : $y;
my $value = '';
if ($x eq 'yellow' and $y eq 'orange'){
$value = 'col1fl0ur';
}
return $value;
}
1
Then in your Main program, you can do the things you like:
use Tst;
my $a = Tst->new('yellow');
my $b = Tst->new('orange');
my $c = $a + $b;
say $c;
This prints out col1fl0ur.

Answer 3

Rather than assigning values to Perl variables ($a, $b, $c, etc.) you might consider creating a data structure that will suit your purposes (whatever they may be!?!). Borodin's answer takes a partial step in that direction.
This example takes that idea a bit farther: the terms in your "mathematical" system would not be linked to individual Perl variables; instead they would be components of a larger data structure.
use strict;
use warnings;
my %xs = (
a => 'yellow',
b => 'orange',
c => 'col1fl0ur',
d => 'foo',
e => 'bar',
f => 'fubb',
g => 'blub',
);
$xs{'a + b'} = $xs{c};
$xs{'a * c'} = $xs{d};
$xs{'d / c'} = $xs{f};
$xs{'a + b - d + f'} = $xs{g};
printf("%15s = %s\n", $_, $xs{$_}) for sort keys %xs;
Output:
a = yellow
a * c = foo
a + b = col1fl0ur
a + b - d + f = blub
b = orange
c = col1fl0ur
d = foo
d / c = fubb
e = bar
f = fubb
g = blub