1Array::Compare(3) User Contributed Perl Documentation Array::Compare(3)
2
6 Array::Compare - Perl extension for comparing arrays.
7
9 use Array::Compare;
10 my $comp1 = Array::Compare->new;
12 $comp->Sep('⎪');
13 $comp->Skip({3 => 1, 4 => 1});
14 $comp->WhiteSpace(0);
15 $comp->Case(1);
16 my $comp2 = Array::Compare->new(Sep => '⎪',
18 WhiteSpace => 0,
19 Case => 1,
20 Skip => {3 => 1, 4 => 1});
21 my @arr1 = 0 .. 10;
23 my @arr2 = 0 .. 10;
24 $comp1->compare(\@arr1, \@arr2);
26 $comp2->compare(\@arr1, \@arr2);
27
29 If you have two arrays and you want to know if they are the same or
30 different, then Array::Compare will be useful to you.
31 All comparisons are carried out via a comparator object. In the sim‐
33 plest usage, you can create and use a comparator object like this:
34 my @arr1 = 0 .. 10;
36 my @arr2 = 0 .. 10;
37 my $comp = Array::Compare->new;
39 if ($comp->compare(\@arr1, \@arr2)) {
41 print "Arrays are the same\n";
42 } else {
43 print "Arrays are different\n";
44 }
45 Notice that you pass references to the two arrays to the comparison
47 method.
48 Internally the comparator compares the two arrays by using "join" to
50 turn both arrays into strings and comparing the strings using "eq". In
51 the joined strings, the elements of the original arrays are separated
52 with the "^G" character. This can cause problems if your array data
53 contains "^G" characters as it is possible that two different arrays
54 can be converted to the same string.
55 To avoid this, it is possible to override the default separator charac‐
57 ter, either by passing and alternative to the "new" function
58 my $comp = Array::Compare->new(Sep => '⎪');
60 or by changing the seperator for an existing comparator object
62 $comp->Sep('⎪');
64 In general you should choose a separator character that won't appear in
66 your data.
67 You can also control whether or not whitespace within the elements of
69 the arrays should be considered significant when making the comparison.
70 The default is that all whitespace is significant. The alternative is
71 for all consecutive white space characters to be converted to a single
72 space for the pruposes of the comparison. Again, this can be turned on
73 when creating a comparator object:
74 my $comp = Array::Compare->new(WhiteSpace => 0);
76 or by altering an existing object:
78 $comp->WhiteSpace(0);
80 You can also control whether or not the case of the data is significant
82 in the comparison. The default is that the case of data is taken into
83 account. This can be changed in the standard ways when creating a new
84 comparator object:
85 my $comp = Array::Compare->new(Case => 0);
87 or by altering an existing object:
89 $comp->Case(0);
91 In addition to the simple comparison described above (which returns
93 true if the arrays are the same and false if they're different) there
94 is also a full comparison which returns a list containing the indexes
95 of elements which differ between the two arrays. If the arrays are the
96 same it returns an empty list. In scalar context the full comparison
97 returns the length of this list (i.e. the number of elements that dif‐
98 fer). You can access the full comparision in two ways. Firstly, there
99 is a "DefFull" attribute. If this is "true" then a full comparison if
100 carried out whenever the "compare" method is called.
101 my $comp = Array::Compare->new(DefFull => 1);
103 $comp->compare(\@arr1, \@arr2); # Full comparison
104 $comp->DefFull(0);
106 $comp->compare(\@arr1, \@arr2); # Simple comparison
107 $comp->DefFull(1);
109 $comp->compare(\@arr1, \@arr2); # Full comparison again
110 Secondly, you can access the full comparison method directly
112 $comp->full_compare(\@arr1, \@arr2);
114 For symmetry, there is also a direct method to use to call the simple
116 comparison.
117 $comp->simple_compare(\@arr1, \@arr2);
119 The final complication is the ability to skip elements in the compari‐
121 son. If you know that two arrays will always differ in a particular
122 element but want to compare the arrays ignoring this element, you can
123 do it with Array::Compare without taking array slices. To do this, a
124 comparator object has an optional attribute called "Skip" which is a
125 reference to a hash. The keys in this hash are the indexes of the array
126 elements and the values should be any true value for elements that
127 should be skipped.
128 For example, if you want to compare two arrays, ignoring the values in
130 elements two and four, you can do something like this:
131 my %skip = (2 => 1, 4 => 1);
133 my @a = (0, 1, 2, 3, 4, 5);
134 my @b = (0, 1, X, 3, X, 5);
135 my $comp = Array::Compare->new(Skip => \%skip);
137 $comp->compare(\@a, \@b);
139 This should return true, as we are explicitly ignoring the columns
141 which differ.
142 Of course, having created a comparator object with no skip hash, it is
144 possible to add one later:
145 $comp->Skip({1 => 1, 2 => 1});
147 or:
149 my %skip = (1 => 1, 2 => 2);
151 $comp->Skip(\%skip);
152 To reset the comparator so that no longer skips elements, set the skip
154 hash to an empty hash.
155 $comp->Skip({});
157 You can also check to see if one array is a permutation of another,
159 i.e. they contain the same elements but in a different order.
160 if ($comp->perm(\@a, \@b) {
162 print "Arrays are perms\n";
163 else {
164 print "Nope. Arrays are completely different\n";
165 }
166 In this case the values of "WhiteSpace" and "Case" are still used, but
168 "Skip" is ignored for, hopefully, obvious reasons.
169
171 new [ %OPTIONS ]
172 Constructs a new comparison object.
174 Takes an optional hash containing various options that control how com‐
176 parisons are carried out. Any omitted options take useful defaults.
177 Sep This is the value that is used to separate fields when the array is
179 joined into a string. It should be a value which doesn't appear in
180 your data. Default is '^G'.
181 WhiteSpace
183 Flag that indicates whether or not whitespace is significant in the
184 comparison. If this value is true then all multiple whitespace
185 characters are changed into a single space before the comparison
186 takes place. Default is 1 (whitespace is significant).
187 Case
189 Flag that indicates whther or not the case of the data should be
190 significant in the comparison. Default is 1 (case is significant).
191 Skip
193 a reference to a hash which contains the numbers of any columns
194 that should be skipped in the comparison. Default is an empty hash
195 (all columns are significant).
196 DefFull
198 Flag which indicates whether the default comparison is simple (just
199 returns true if the arrays are the same or false if they're not) or
200 full (returns an array containing the indexes of the columns that
201 differ). Default is 0 (simple comparison).
202 compare_len \@ARR1, \@ARR2
204 Very simple comparison. Just checks the lengths of the arrays are the
206 same.
207 compare \@ARR1, \@ARR2
209 Compare the values in two arrays and return a data indicating whether
211 the arrays are the same. The exact return values differ depending on
212 the comparison method used. See the descriptions of simple_compare and
213 full_compare for details.
214 Uses the value of DefFull to determine which comparison routine to use.
216 simple_compare \@ARR1, \@ARR2
218 Compare the values in two arrays and return a flag indicating whether
220 or not the arrays are the same.
221 Returns true if the arrays are the same or false if they differ.
223 Uses the values of 'Sep', 'WhiteSpace' and 'Skip' to influence the com‐
225 parison.
226 full_compare \@ARR1, \@ARR2
228 Do a full comparison between two arrays.
230 Checks each individual column. In scalar context returns the number of
232 columns that differ (zero if the arrays are the same). In list context
233 returns an list containing the indexes of the columns that differ (an
234 empty list if the arrays are the same).
235 Uses the values of 'Sep' and 'WhiteSpace' to influence the comparison.
237 Note: If the two arrays are of different lengths then this method just
239 returns the indexes of the elements that appear in one array but not
240 the other (i.e. the indexes from the longer array that are beyond the
241 end of the shorter array). This might be a little counter-intuitive.
242 perm \@ARR1, \@ARR2
244 Check to see if one array is a permutation of the other (i.e. contains
246 the same set of elements, but in a different order).
247 We do this by sorting the arrays and passing references to the assorted
249 versions to simple_compare. There are also some small changes to sim‐
250 ple_compare as it should ignore the Skip hash if we are called from
251 perm.
252
254 Dave Cross <dave@mag-sol.com>
255
257 perl(1).
258
260 Copyright (C) 2000-2005, Magnum Solutions Ltd. All Rights Reserved.
261 This script is free software; you can redistribute it and/or modify it
263 under the same terms as Perl itself.
264perl v5.8.8 2007-04-05 Array::Compare(3)