#!/usr/bin/perl -w
# Example 1: Solve  y'' + 2y' + y = 0, y(0) = 0, y'(0) = 1
#            Solution: y = x*exp(-x)
use Math::ODE;
my $o = new Math::ODE ( file => 'data',
                        step => 0.1,
                        initial => [0,1], 
                        ODE => [ \&DE1, \&DE2 ], 
                        t0 => 0,
                        tf => 10 );
$o->evolve;
system("gnuplot -persist gnuplot.2");
# y'' + 2y' + y = 0
sub DE1 { my ($t,$y) = @_; return $y->[1]; }
sub DE2 { my ($t,$y) = @_; return -2 * $y->[1] - $y->[0]; }