NAME

Test::Number::Delta - Compare if the difference between two numbers is within a specified precision

SYNOPSIS

# Default precision
use Test::Number::Delta;
delta_ok( 1e-5, 2e-5, 'values within 1e-6'); # not ok

# Specific precision for a single test
delta_within( 1e-3, 2e-3, 1e-4, 'values within 1e-4'); not ok

# Set a different default precision
use Test::Number::Delta within => 1e-5;
delta_ok( 1e-5, 2e-5, 'values within 1e-5'); # ok

DESCRIPTION

Most programmers at one time or another are confronted with the issue of comparing floating-point numbers for equality. The canonical idiom is to test if the absolute value of the difference of the numbers is within a desired precision. This module provides such a function for use with Test::Harness. Usage is similar to other test functions described in Test::More. Semantically, the delta_within function replaces this kind of construct:

ok ( abs($p - $q) <= $precision, '$p is equal to $q' ) or
    diag "$p is not equal to $q to within $precision";

While there's nothing wrong with that construct, it's a pain to type it repeatedly in a test script. This module does the same thing with a single function call. The delta_ok function is similar, but uses a global default precision so even the precision need not be specified repeatedly. Both functions are exported automatically.

USAGE

Setting the default precision

By default, use Test::Number::Delta will compare equality with a precision of 1e-6. (An arbitrary choice on my part.) To specific a different precision, provide a within parameter when importing the module with use:

use Test::Number::Delta within => 1e-9;

delta_within

delta_within( $p, $q, $prec, '$p and $q are equal within $prec' );

This test compares equality within a given precision. The test is true if the absolute value of the difference between $p and $q is less than or equal to the precision. If the test is true, it prints an "OK" statement for use in testing. If the test is not true, this function prints a failure report and diagnostic.

delta_ok

delta_ok( $p, $q, '$p and $q are equal' );

This test compares equality within the default precision specified during import (or the default of 1e-6). The test is true if the absolute value of the difference between $p and $q is less than or equal to the default precision. If the test is true, it prints an "OK" statement for use in testing. If the test is not true, this function prints a failure report and diagnostic.

BUGS

Please report bugs using the CPAN Request Tracker at http://rt.cpan.org/NoAuth/Bugs.html?Dist=Test-Number-Delta

AUTHOR

David A. Golden (DAGOLDEN)

david@dagolden.com

http://dagolden.com/

COPYRIGHT

Copyright (c) 2005 by David A. Golden

This program is free software; you can redistribute it and/or modify it under the same terms as Perl itself.

The full text of the license can be found in the LICENSE file included with this module.

SEE ALSO

Test::More, Test::Harness, Test::Builder