1Test::Number::Delta(3)User Contributed Perl DocumentationTest::Number::Delta(3)
2
6 Test::Number::Delta - Compare the difference between numbers against a
7 given tolerance
8
10 version 1.06
11
13 # Import test functions
14 use Test::Number::Delta;
15 # Equality test with default tolerance
17 delta_ok( 1e-5, 2e-5, 'values within 1e-6');
18 # Inequality test with default tolerance
20 delta_not_ok( 1e-5, 2e-5, 'values not within 1e-6');
21 # Provide specific tolerance
23 delta_within( 1e-3, 2e-3, 1e-4, 'values within 1e-4');
24 delta_not_within( 1e-3, 2e-3, 1e-4, 'values not within 1e-4');
25 # Compare arrays or matrices
27 @a = ( 3.14, 1.41 );
28 @b = ( 3.15, 1.41 );
29 delta_ok( \@a, \@b, 'compare @a and @b' );
30 # Set a different default tolerance
32 use Test::Number::Delta within => 1e-5;
33 delta_ok( 1.1e-5, 2e-5, 'values within 1e-5'); # ok
34 # Set a relative tolerance
36 use Test::Number::Delta relative => 1e-3;
37 delta_ok( 1.01, 1.0099, 'values within 1.01e-3');
38
40 At some point or another, most programmers find they need to compare
41 floating-point numbers for equality. The typical idiom is to test if
42 the absolute value of the difference of the numbers is within a desired
43 tolerance, usually called epsilon. This module provides such a
44 function for use with Test::More. Usage is similar to other test
45 functions described in Test::More. Semantically, the "delta_within"
46 function replaces this kind of construct:
47 ok ( abs($p - $q) < $epsilon, '$p is equal to $q' ) or
49 diag "$p is not equal to $q to within $epsilon";
50 While there's nothing wrong with that construct, it's painful to type
52 it repeatedly in a test script. This module does the same thing with a
53 single function call. The "delta_ok" function is similar, but either
54 uses a global default value for epsilon or else calculates a 'relative'
55 epsilon on the fly so that epsilon is scaled automatically to the size
56 of the arguments to "delta_ok". Both functions are exported
57 automatically.
58 Because checking floating-point equality is not always reliable, it is
60 not possible to check the 'equal to' boundary of 'less than or equal to
61 epsilon'. Therefore, Test::Number::Delta only compares if the absolute
62 value of the difference is less than epsilon (for equality tests) or
63 greater than epsilon (for inequality tests).
64
66 use Test::Number::Delta;
67 With no arguments, epsilon defaults to 1e-6. (An arbitrary choice on
68 the author's part.)
69 use Test::Number::Delta within => 1e-9;
71 To specify a different default value for epsilon, provide a "within"
72 parameter when importing the module. The value must be non-zero.
73 use Test::Number::Delta relative => 1e-3;
75 As an alternative to using a fixed value for epsilon, provide a
76 "relative" parameter when importing the module. This signals that
77 "delta_ok" should test equality with an epsilon that is scaled to the
78 size of the arguments. Epsilon is calculated as the relative value
79 times the absolute value of the argument with the greatest magnitude.
80 Mathematically, for arguments 'x' and 'y':
81 epsilon = relative * max( abs(x), abs(y) )
83 For example, a relative value of "0.01" would mean that the arguments
85 are equal if they differ by less than 1% of the larger of the two
86 values. A relative value of 1e-6 means that the arguments must differ
87 by less than 1 millionth of the larger value. The relative value must
88 be non-zero.
89 Combining with a test plan
91 use Test::Number::Delta 'no_plan';
92 # or
94 use Test::Number::Delta within => 1e-9, tests => 1;
96 If a test plan has not already been specified, the optional parameter
98 for Test::Number::Delta may be followed with a test plan (see
99 Test::More for details). If a parameter for Test::Number::Delta is
100 given, it must come first.
101
103 delta_within
104 delta_within( $p, $q, $epsilon, '$p and $q are equal within $epsilon' );
105 delta_within( \@p, \@q, $epsilon, '@p and @q are equal within $epsilon' );
106 This function tests for equality within a given value of epsilon. The
108 test is true if the absolute value of the difference between $p and $q
109 is less than epsilon. If the test is true, it prints an "OK" statement
110 for use in testing. If the test is not true, this function prints a
111 failure report and diagnostic. Epsilon must be non-zero.
112 The values to compare may be scalars or references to arrays. If the
114 values are references to arrays, the comparison is done pairwise for
115 each index value of the array. The pairwise comparison is recursive,
116 so matrices may be compared as well.
117 For example, this code sample compares two matrices:
119 my @a = ( [ 3.14, 6.28 ],
121 [ 1.41, 2.84 ] );
122 my @b = ( [ 3.14, 6.28 ],
124 [ 1.42, 2.84 ] );
125 delta_within( \@a, \@b, 1e-6, 'compare @a and @b' );
127 The sample prints the following:
129 not ok 1 - compare @a and @b
131 # At [1][0]: 1.4100000 and 1.4200000 are not equal to within 0.000001
132 delta_ok
134 delta_ok( $p, $q, '$p and $q are close enough to equal' );
135 delta_ok( \@p, \@q, '@p and @q are close enough to equal' );
136 This function tests for equality within a default epsilon value. See
138 "USAGE" for details on changing the default. Otherwise, this function
139 works the same as "delta_within".
140 delta_not_within
142 delta_not_within( $p, $q, '$p and $q are different' );
143 delta_not_within( \@p, \@q, $epsilon, '@p and @q are different' );
144 This test compares inequality in excess of a given value of epsilon.
146 The test is true if the absolute value of the difference between $p and
147 $q is greater than epsilon. For array or matrix comparisons, the test
148 is true if any pair of values differs by more than epsilon. Otherwise,
149 this function works the same as "delta_within".
150 delta_not_ok
152 delta_not_ok( $p, $q, '$p and $q are different' );
153 delta_not_ok( \@p, \@q, '@p and @q are different' );
154 This function tests for inequality in excess of a default epsilon
156 value. See "USAGE" for details on changing the default. Otherwise,
157 this function works the same as "delta_not_within".
158
160 · Number::Tolerant
161 · Test::Deep::NumberTolerant
163
165 Bugs / Feature Requests
166 Please report any bugs or feature requests through the issue tracker at
167 <https://github.com/dagolden/Test-Number-Delta/issues>. You will be
168 notified automatically of any progress on your issue.
169 Source Code
171 This is open source software. The code repository is available for
172 public review and contribution under the terms of the license.
173 <https://github.com/dagolden/Test-Number-Delta>
175 git clone https://github.com/dagolden/Test-Number-Delta.git
177
179 David Golden <dagolden@cpan.org>
180
182 This software is Copyright (c) 2014 by David Golden.
183 This is free software, licensed under:
185 The Apache License, Version 2.0, January 2004
187perl v5.28.0 2014-11-25 Test::Number::Delta(3)