File Coverage

blib/lib/Math/Erf/Approx.pm

Criterion	Covered	Total	%
statement	49	53	92.4
branch	2	4	50.0
condition	1	2	50.0
subroutine	13	13	100.0
pod	3	3	100.0
total	68	75	90.6

package Math::Erf::Approx;

use 5.010;
use strict;
use warnings;
use Scalar::Util qw< blessed >;
use Sub::Exporter -setup => { exports => [qw< erf erfc >] };
use Test::More;

BEGIN {
	no warnings 'once';
	$Math::Erf::Approx::AUTHORITY = 'cpan:TOBYINK';
	$Math::Erf::Approx::VERSION   = '0.001';
};

sub erf
{
	my ($x) = @_;

	if ($x < 0)
	{
		return -erf(-$x);
	}

	my @a = qw< 1.0 0.278393 0.230389 0.000972 0.078108>;

	my $sum;
	for my $i (0 .. 4)
	{
		$sum += $a[$i] * ($x ** $i);
	}

	1.0 - ($sum ** -4);
}

sub erfc
{
	my ($x, $erf) = @_;
	$erf //= \&erf;
	1.0 - $erf->($x);
}


sub _test_cases
{
	my @numbers = grep { /\d/ } split /\s+/, q{
0.00	0.0000000	1.0000000	1.30	0.9340079	0.0659921
0.05	0.0563720	0.9436280	1.40	0.9522851	0.0477149
0.10	0.1124629	0.8875371	1.50	0.9661051	0.0338949
0.15	0.1679960	0.8320040	1.60	0.9763484	0.0236516
0.20	0.2227026	0.7772974	1.70	0.9837905	0.0162095
0.25	0.2763264	0.7236736	1.80	0.9890905	0.0109095
0.30	0.3286268	0.6713732	1.90	0.9927904	0.0072096
0.35	0.3793821	0.6206179	2.00	0.9953223	0.0046777
0.40	0.4283924	0.5716076	2.10	0.9970205	0.0029795
0.45	0.4754817	0.5245183	2.20	0.9981372	0.0018628
0.50	0.5204999	0.4795001	2.30	0.9988568	0.0011432
0.55	0.5633234	0.4366766	2.40	0.9993115	0.0006885
0.60	0.6038561	0.3961439	2.50	0.9995930	0.0004070
0.65	0.6420293	0.3579707	2.60	0.9997640	0.0002360
0.70	0.6778012	0.3221988	2.70	0.9998657	0.0001343
0.75	0.7111556	0.2888444	2.80	0.9999250	0.0000750
0.80	0.7421010	0.2578990	2.90	0.9999589	0.0000411
0.85	0.7706681	0.2293319	3.00	0.9999779	0.0000221
0.90	0.7969082	0.2030918	3.10	0.9999884	0.0000116
0.95	0.8208908	0.1791092	3.20	0.9999940	0.0000060
1.00	0.8427008	0.1572992	3.30	0.9999969	0.0000031
1.10	0.8802051	0.1197949	3.40	0.9999985	0.0000015
1.20	0.9103140	0.0896860	3.50	0.9999993	0.0000007
	};

	my @test_cases;
	while (@numbers)
	{
		push @test_cases, [shift @numbers, shift @numbers, shift @numbers];
	}

	return @test_cases;
}

sub _close_enough
{
	my ($x, $y) = @_;
	my $err = abs($x - $y);
	return 1 if $err < 0.0005;
	diag "Got:     $x";
	diag "Expected $y";
	return;
}

sub run_tests
{
	my ($class) = @_;
	my @cases = $class->_test_cases;

	plan tests => (2 * @cases);

	foreach my $tc (@cases)
	{
		my ($x, $erf, $erfc) = @$tc;
		ok _close_enough(erf($x), $erf), "erf($x)";
		ok _close_enough(erfc($x), $erfc), "erfc($x)";
	}
}

caller(0) or __PACKAGE__->run_tests;
__END__