NAME

Test::Approx - compare two things for approximate equality

SYNOPSIS

  use Test::Approx 'no_plan';

  is_approx( 'abcd', 'abcd', 'equal strings' );
  is_approx( 1234, 1234, 'equal integers' );
  is_approx( 1.234, 1.234, 'equal decimal numbers' );
  is_approx( '1.234000', '1.234', 'equal decimal numbers, extra zeros' );
  is_approx( 1.0, 1, 'equal decimal number & integer' );

  is_approx( 'abcdefgh', 'abcdefg', 'approx strings' );
  is_approx( 1, 1.001, 'approx given decimal number & integer' );
  is_approx( 51.60334, 51.603335, 'approx decimal numbers' );

  # default Levenshtein edit tolerance is 5% of avg string length:
  is_approx( 'abcdefg', 'abcgfe', 'str tolerance' ); # fail

  # default difference tolerance is 5% of first number:
  is_approx( 1, 1.04, 'num tolerance' ); # fail
  is_approx( 1, 1.05, 'num tolerance' ); # fail

  # default difference tolerance is 5% of first integer, or 1:
  is_approx( 1, 2, 'int tolerance' ); # pass
  is_approx( 100, 105, 'int tolerance' ); # pass
  is_approx( 100, 106, 'int tolerance' ); # fail

  # you can set the tolerance yourself:
  is_approx( 'abcdefg', 'abcgfe', 'diff strings', '50%' ); # pass

  # you can set tolerance as a number too:
  is_approx( 'abcdefg', 'abcgfe', 'diff strings', 6 );

  # you can force compare as string, number, or integer:
  is_approx_str( '1.001', '1.901', 'pass as string' );
  is_approx_num( '1.001', '1.901', 'fail as num' );
  is_approx_int( '1.001', '1.901', 'pass as int' ); # not rounded!

DESCRIPTION

This module lets you test if two things are approximately equal. Yes, that sounds a bit wrong at first - surely you know if they should be equal or not? But there are actually valid cases when you don't / can't know. This module is meant for those rare cases when close is good enough.

FUNCTIONS

is_approx( $arg1, $arg2 [, $test_name, $tolerance ] )

Tests if two scalars $arg1 & $arg2 are approximately equal by using one of: "is_approx_str", "is_approx_num" or is_approx_int.

$test_name defaults to 'arg1' =~ 'arg2'.

$tolerance is used to determine how different the scalars can be, it defaults to 5%. It can also be set as a number representing a threshold. To determine which:

  $tolerance = '6%'; # threshold = calculated at 6%
  $tolerance = 0.06; # threshold = 0.06

See the individual functions to determine how $tolerance is used.

is_approx_str( $str1, $str2 [, $test_name, $tolerance ] )

Tests if $str1 is approximately equal to $str2 by using Text::LevenshteinXS to compute the edit distance between the two strings, and comparing that to $tolerance.

$tolerance is used to determine how many edits are allowed before the comparison test fails. If a percentage is given, the edit distance threshold will be set to x% of the average lengths of the two strings. eg:

  $edit_threshold = int( $x_percent * avg(length($str1), length($str2)) );

If that's less than 0, it defaults to 1. You can also pass $tolerance in as an number. To avoid confusion:

  $tolerance = '6%'; # threshold = 6% of avg strlen
  $tolerance = 0.06; # threshold = int( 0.06 ) = 0

is_approx_num( $num1, $num2 [, $test_name, $tolerance ] )

Tests if $num1 is approximately equal to $num2 by calculating the distance between them and comparing that to $tolerance.

If $tolerance is a percentage, the distance threshold will be set to x% of the first number, eg:

  $threshold = $x_percent * $num1;

Note that this can be 0 > $t > 1, which is probably what you want. To avoid confusion:

  $tolerance = '6%'; # threshold = 6% of $num1
  $tolerance = 0.06; # threshold = 0.06

is_approx_int( $int1, $int2 [, $test_name, $tolerance ] )

Tests if $int1 is approximately equal to $int2 by calculating the distance between them and comparing that to $tolerance. This is slightly different to "is_approx_num" as all fractions are removed.

If $tolerance is a percentage, the distance threshold will be set to x% of the first integer, or 1. Eg:

  $threshold = int( $x_percent * $int1 ) || 1;

To avoid confusion:

  $tolerance = '6%'; # threshold = 6% of $int1
  $tolerance = 0.06; # threshold = 0.06

EXPORTS

is_approx, is_approx_str, is_approx_num, is_approx_int

AUTHOR

Steve Purkis <spurkis@cpan.org>

COPYRIGHT

Copyright (c) 2008-2010 Steve Purkis. Released under the same terms as Perl itself.

SEE ALSO

Text::LevenshteinXS, Test::Builder