Hello all. I'm new to Perl, and really new to programming in general - I'm an sysadmin by trade (please don't hold that against me). Inspired by the Hanoi towers node, I wrote this as an learning exercise on recursive subroutines.

It's really a simple function, it prompts you for n, and then calculates (x + y)^n and expands it out as you would in an algebra 101 class, using binomial theorem. I welcome any comments, suggestions or opinions. I'd like to know if there's a better way to format the output other than running it through a bunch of regex's. I know it's not the prettiest code, but bear with me:


#!/usr/bin/perl

use strict;
use warnings;
my ($power, $result);

sub binomial_power 
{
    my ($c, $xp, $yp) = @_;
    $result .= $c . "x^" . $xp . "y^" . ($yp - 1) . " + ";
    if ($yp <= $power ) { binomial_power ((($c * $xp)/$yp), ($xp-1), (
+$yp+1));}
}

# Get the input
print "\nEnter the power: ";
chomp($power = (<STDIN>));

# Do the work
binomial_power (1, $power, 1);

# Make it pretty
$result =~ s/1x/x/g;
$result =~ s/x\^1/x/g;
$result =~ s/y\^1/y/g;
$result =~ s/x\^0//g;
$result =~ s/y\^0//g;


# And print it out
print "The result is: \n(x + y)^$power = $result\n";

[download]

For reference - $c is the coefficient, $xp is the exponent of x, and $yp is the exponent of y

In reply to Algebraic Expansion of Binomials Using a Recursive Subroutine by lilgreen

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