Array::Compare(3) User Contributed Perl Documentation Array::Compare(3)NAMEArray::Compare - Perl extension for comparing arrays.
SYNOPSIS
use Array::Compare;
my $comp1 = Array::Compare->new;
$comp->Sep('|');
$comp->Skip({3 => 1, 4 => 1});
$comp->WhiteSpace(0);
$comp->Case(1);
my $comp2 = Array::Compare->new(Sep => '|',
WhiteSpace => 0,
Case => 1,
Skip => {3 => 1, 4 => 1});
my @arr1 = 0 .. 10;
my @arr2 = 0 .. 10;
$comp1->compare(\@arr1, \@arr2);
$comp2->compare(\@arr1, \@arr2);
DESCRIPTION
If you have two arrays and you want to know if they are the same or
different, then Array::Compare will be useful to you.
All comparisons are carried out via a comparator object. In the
simplest usage, you can create and use a comparator object like this:
my @arr1 = 0 .. 10;
my @arr2 = 0 .. 10;
my $comp = Array::Compare->new;
if ($comp->compare(\@arr1, \@arr2)) {
print "Arrays are the same\n";
} else {
print "Arrays are different\n";
}
Notice that you pass references to the two arrays to the comparison
method.
Internally the comparator compares the two arrays by using "join" to
turn both arrays into strings and comparing the strings using "eq". In
the joined strings, the elements of the original arrays are separated
with the "^G" character. This can cause problems if your array data
contains "^G" characters as it is possible that two different arrays
can be converted to the same string.
To avoid this, it is possible to override the default separator
character, either by passing and alternative to the "new" function
my $comp = Array::Compare->new(Sep => '|');
or by changing the seperator for an existing comparator object
$comp->Sep('|');
In general you should choose a separator character that won't appear in
your data.
You can also control whether or not whitespace within the elements of
the arrays should be considered significant when making the comparison.
The default is that all whitespace is significant. The alternative is
for all consecutive white space characters to be converted to a single
space for the pruposes of the comparison. Again, this can be turned on
when creating a comparator object:
my $comp = Array::Compare->new(WhiteSpace => 0);
or by altering an existing object:
$comp->WhiteSpace(0);
You can also control whether or not the case of the data is significant
in the comparison. The default is that the case of data is taken into
account. This can be changed in the standard ways when creating a new
comparator object:
my $comp = Array::Compare->new(Case => 0);
or by altering an existing object:
$comp->Case(0);
In addition to the simple comparison described above (which returns
true if the arrays are the same and false if they're different) there
is also a full comparison which returns a list containing the indexes
of elements which differ between the two arrays. If the arrays are the
same it returns an empty list. In scalar context the full comparison
returns the length of this list (i.e. the number of elements that
differ). You can access the full comparision in two ways. Firstly,
there is a "DefFull" attribute. If this is "true" then a full
comparison if carried out whenever the "compare" method is called.
my $comp = Array::Compare->new(DefFull => 1);
$comp->compare(\@arr1, \@arr2); # Full comparison
$comp->DefFull(0);
$comp->compare(\@arr1, \@arr2); # Simple comparison
$comp->DefFull(1);
$comp->compare(\@arr1, \@arr2); # Full comparison again
Secondly, you can access the full comparison method directly
$comp->full_compare(\@arr1, \@arr2);
For symmetry, there is also a direct method to use to call the simple
comparison.
$comp->simple_compare(\@arr1, \@arr2);
The final complication is the ability to skip elements in the
comparison. If you know that two arrays will always differ in a
particular element but want to compare the arrays ignoring this
element, you can do it with Array::Compare without taking array slices.
To do this, a comparator object has an optional attribute called "Skip"
which is a reference to a hash. The keys in this hash are the indexes
of the array elements and the values should be any true value for
elements that should be skipped.
For example, if you want to compare two arrays, ignoring the values in
elements two and four, you can do something like this:
my %skip = (2 => 1, 4 => 1);
my @a = (0, 1, 2, 3, 4, 5);
my @b = (0, 1, X, 3, X, 5);
my $comp = Array::Compare->new(Skip => \%skip);
$comp->compare(\@a, \@b);
This should return true, as we are explicitly ignoring the columns
which differ.
Of course, having created a comparator object with no skip hash, it is
possible to add one later:
$comp->Skip({1 => 1, 2 => 1});
or:
my %skip = (1 => 1, 2 => 2);
$comp->Skip(\%skip);
To reset the comparator so that no longer skips elements, set the skip
hash to an empty hash.
$comp->Skip({});
You can also check to see if one array is a permutation of another,
i.e. they contain the same elements but in a different order.
if ($comp->perm(\@a, \@b) {
print "Arrays are perms\n";
else {
print "Nope. Arrays are completely different\n";
}
In this case the values of "WhiteSpace" and "Case" are still used, but
"Skip" is ignored for, hopefully, obvious reasons.
METHODS
new [ %OPTIONS ]
Constructs a new comparison object.
Takes an optional hash containing various options that control how
comparisons are carried out. Any omitted options take useful defaults.
Sep This is the value that is used to separate fields when the array is
joined into a string. It should be a value which doesn't appear in
your data. Default is '^G'.
WhiteSpace
Flag that indicates whether or not whitespace is significant in the
comparison. If this value is true then all multiple whitespace
characters are changed into a single space before the comparison
takes place. Default is 1 (whitespace is significant).
Case
Flag that indicates whther or not the case of the data should be
significant in the comparison. Default is 1 (case is significant).
Skip
a reference to a hash which contains the numbers of any columns
that should be skipped in the comparison. Default is an empty hash
(all columns are significant).
DefFull
Flag which indicates whether the default comparison is simple (just
returns true if the arrays are the same or false if they're not) or
full (returns an array containing the indexes of the columns that
differ). Default is 0 (simple comparison).
compare_len \@ARR1, \@ARR2
Very simple comparison. Just checks the lengths of the arrays are the
same.
compare \@ARR1, \@ARR2
Compare the values in two arrays and return a data indicating whether
the arrays are the same. The exact return values differ depending on
the comparison method used. See the descriptions of simple_compare and
full_compare for details.
Uses the value of DefFull to determine which comparison routine to use.
simple_compare \@ARR1, \@ARR2
Compare the values in two arrays and return a flag indicating whether
or not the arrays are the same.
Returns true if the arrays are the same or false if they differ.
Uses the values of 'Sep', 'WhiteSpace' and 'Skip' to influence the
comparison.
full_compare \@ARR1, \@ARR2
Do a full comparison between two arrays.
Checks each individual column. In scalar context returns the number of
columns that differ (zero if the arrays are the same). In list context
returns an list containing the indexes of the columns that differ (an
empty list if the arrays are the same).
Uses the values of 'Sep' and 'WhiteSpace' to influence the comparison.
Note: If the two arrays are of different lengths then this method just
returns the indexes of the elements that appear in one array but not
the other (i.e. the indexes from the longer array that are beyond the
end of the shorter array). This might be a little counter-intuitive.
perm \@ARR1, \@ARR2
Check to see if one array is a permutation of the other (i.e. contains
the same set of elements, but in a different order).
We do this by sorting the arrays and passing references to the assorted
versions to simple_compare. There are also some small changes to
simple_compare as it should ignore the Skip hash if we are called from
perm.
AUTHOR
Dave Cross <dave@mag-sol.com>
SEE ALSOperl(1).
COPYRIGHT AND LICENSE
Copyright (C) 2000-2005, Magnum Solutions Ltd. All Rights Reserved.
This script is free software; you can redistribute it and/or modify it
under the same terms as Perl itself.
perl v5.14.1 2011-07-21 Array::Compare(3)