NAME

Test::Approximate - test for approximate numeric equality

VERSION

version 0.102

SYNOPSIS

    use Test::Approximate;

    set_dop(3); # this is the default value
    is_approx 3, 3.001, 'close enough';

    set_dop(1);
    is_approx 3.0, 3.4, 'also close enough';

    set_dop(2);
    isnt_approx 3.0, 3.4, 'different';

DESCRIPTION

Test::Approximate provides tests that can be used to compare floating-point numbers for approximate equality (is_approx()) and inequality (isnt_approx()). This is achieved using the concept of digits of precision, or DOP. The DOP of a number are a fixed number of significant digits of that number. For example, with 3 DOP 1,234,000 would be 1,230,000 and 0.000 1234 would be 0.000 123.

By default, 3 DOP are used.

METHOD

To compare the two numbers $actual and $expected, a (power-of-ten) scaling factor for $expected is determined, such that, when multiplied by it, there will be DOP digits before the decimal point. The absolute value of the difference between $actual and $expected is multiplied by the scaling factor and rounded to the nearest integer. If this value is zero, the two values are deemed to be approximately the same (or non-zero in the case of isnt_approx()).

DIAGNOSTICS

is_approx() and isnt_approx() will emit diagnostics whenever a test fails.

For example,

    set_dop(2);
    is_approx 1000,1100; # fails

produces the following output:

    not ok 1
    # Failed test at ... line 13.
    #     Original: 1000, 1100
    #     DOP: 2
    #     Delta: 100
    #     Multiplier: 0.01 (1e-2)
    #     Diff: round(1)
    #     Comparison: 1 == 0

Original: the untouched values of $actual and $expected as passed in to the test.

DOP: the digits of precision used.

Delta: the absolute difference between $actual and $expected.

Multiplier: factor used to make all DOP occur before the decimal point.

Diff: delta after scaling.

Comparison: the comparison used for the test.

FUNCTIONS

is_approx

    is_approx $actual, $expected, $name;

Compares $actual to $expected as described above and generates an appropriate standard pass/fail test result. As is usual with Perl testing modules, $name is optional.

isnt_approx

    isnt_approx $actual, $expected, $name;

The opposite of is_approx(). The test will pass if $actual and $expected are sufficiently different.

set_dop($new_dop)

    set_dop(4);      # set precision to 4 DOP
    print set_dop(); # 4

set_dop() is used to set the precision of is_approx() and isnt_approx(). It takes a single, optional, argument that represents the DOP to use in the comparisons. $new_dop must be an integer between 1 and 14 inclusive and will be shoehorned into that range if necessary. $new_dop is returned as the value of the function.

If $new_dop is absent, set_dop just returns the current value of DOP.

See DESCRIPTION above for more about DOP.

AUTHOR & COPYRIGHT

Copyright 2020 by Brian Greenfield < briang @ cpan dot org >.

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

cpanm Test::Approximate

perl -MCPAN -e shell
install Test::Approximate