#!/usr/bin/perl

use strict;
use warnings;

package Range;

sub new {
    my $class       = shift;
    my $lower       = shift;
    my $upper       = shift;
    my $delta       = shift || 0.0001;

    my $self = { 
        lower => $lower,
        upper => $upper,
        delta => $delta,
        current => $lower,
    };
    return bless $self, $class;
}

sub next {
    my $self = shift;
    if ($self->{current} + $self->{delta} < $self->{upper}) {
        $self->{current} += $self->{delta};
        return 1;
    } else {
        return undef;
    }
}

package main;

sub integrate {
    my $function    = shift;
    my $iter        = shift;
    my $sum;
    
    do { 
        $sum += $function->($iter->{current}) * $iter->{delta}; 
    } while ($iter->next());
    return $sum;
}


print sprintf("%.2f", integrate(sub {(shift)**2}, new Range (2, 5))), "\n";