NAME Data::Cmp - Compare two data structures, return -1/0/1 like cmp VERSION This document describes version 0.010 of Data::Cmp (from Perl distribution Data-Cmp), released on 2021-04-12. SYNOPSIS use Data::Cmp qw(cmp_data); cmp_data(["one", "two", "three"], ["one", "two", "three"]); # => 0 cmp_data(["one", "two" , "three"], ["one", "two2", "three"]); # => -1 cmp_data(["one", "two", "three"], ["one", "TWO", "three"]); # => 1 # hash/array is not "comparable" with scalar cmp_data(["one", "two", {}], ["one", "two", "three"]); # => 2 Sort data structures (of similar structures): my @arrays = (["c"], ["b"], ["a", "b"], ["a"], ["a","c"]); my @sorted = sort { cmp_data($a, $b) } @arrays; # => (["a"], ["a","b"], ["a","c"], ["b"], ["c"]) DESCRIPTION This relatively lightweight (no non-core dependencies, under 100 lines of code) module offers the "cmp_data" function that, like Perl's "cmp", returns -1/0/1 value. "cmp_data" differs from "cmp" in that it can compare two data of different types and compare data items recursively, with pretty sensible semantics. In addition to returning -1/0/1, "cmp_data" can also return 2 if two data differ but not comparable: there is no sensible notion of which one is "greater than" the other. An example is empty hash "{}" vs empty array "[]"). This module can handle circular structure. The following are the rules of comparison used by "cmp_data()": * Two undefs are the same cmp_data(undef, undef); # 0 * A defined value is greater than undef cmp_data(undef, 0); # -1 * Two non-reference scalars are compared string-wise using Perl's cmp cmp_data("a", "A"); # 1 cmp_data(10, 9); # -1 * A reference and non-reference are different and not comparable cmp_data([], 0); # 2 * Two references that are of different types are different and not comparable cmp_data([], {}); # 2 * Blessed references that are blessed into different packages are different and not comparable cmp_data(bless([], "foo"), bless([], "bar")); # 2 cmp_data(bless([], "foo"), bless([], "foo")); # 0 * Two array references are compared element by element (unless at least one of the arrayref has been seen, in which case see last rule) cmp_data(["a","b","c"], ["a","b","c"]); # 0 cmp_data(["a","b","c"], ["a","b","d"]); # -1 cmp_data(["a","d","c"], ["a","b","e"]); # 1 * A longer arrayref is greater than its shorter subset cmp_data(["a","b"], ["a"]); # 1 * Two hash references are compared key by key (unless at least one of the hashref has been seen, in which case see last rule) cmp_data({k1=>"a", k2=>"b", k3=>"c"}, {k1=>"a", k2=>"b", k3=>"c"}); # 0 cmp_data({k1=>"a", k2=>"b", k3=>"c"}, {k1=>"a", k2=>"b", k3=>"d"}); # 1 * When two hash references share a common subset of pairs but have non-common pairs, the greater hashref is the one that has more non-common pairs If the number of non-common pairs are the same, they are just different and not comparable: cmp_data({k1=>"", k2=>"", k3=>""}, {k1=>"", k5=>""}); # 1 (hash1 has 2 non-common keys: k2 & k3; hash2 only has 1: k5) cmp_data({k1=>"", k2=>"", k3=>""}, {k1=>"", k5=>"", k6=>", k7=>""}); # -1 (hash1 has 2 non-common keys: k2 & k3; hash2 has 3 non-common pairs: k5, k6, k7) cmp_data({k1=>"", k2=>"", k3=>""}, {k1=>"", k5=>"", k6=>"}); # 2 (both hashes have 2 non-common pairs) * All other types of references (i.e. non-hash, non-array) are the same only if their address is the same; otherwise they are different and not comparable cmp_data(\1, \1); # 2 my $ref = \1; cmp_data($ref, $ref); # 0 * A seen (hash or array) reference is no longer recursed, it's compared by address (see previous rule) my $ary1 = [1]; push @$ary1, $ary1; my $ary2 = [1]; push @$ary2, $ary2; my $ary3 = [1]; push @$ary3, $ary1; cmp_data($ary1, $ary2); # 2 cmp_data($ary1, $ary3); # 0 FUNCTIONS cmp_data Usage: cmp_data($d1, $d2) => -1/0/1/2 HOMEPAGE Please visit the project's homepage at <https://metacpan.org/release/Data-Cmp>. SOURCE Source repository is at <https://github.com/perlancar/perl-Data-Cmp>. BUGS Please report any bugs or feature requests on the bugtracker website <https://github.com/perlancar/perl-Data-Cmp/issues> When submitting a bug or request, please include a test-file or a patch to an existing test-file that illustrates the bug or desired feature. SEE ALSO Data comparison Other variants of Data::Cmp: Data::Cmp::Numeric, Data::Cmp::StrOrNumeric, Data::Cmp::Custom (allows custom actions and comparison routines), Data::Cmp::Diff (generates diff structure instead of just returning -1/0/1/2), Data::Cmp::Diff::Perl (generates diff in the form of Perl code). Modules that just return boolean result ("same or different"): Data::Compare, Test::Deep::NoTest (offers flexibility or approximate or custom comparison). Modules that return some kind of "diff" data: Data::Comparator, Data::Diff. Of course, to check whether two structures are the same you can also serialize each one then compare the serialized strings/bytes. There are many modules for serialization: JSON, YAML, Sereal, Data::Dumper, Storable, Data::Dmp, just to name a few. Test modules that do data structure comparison: Test::DataCmp (test module based on Data::Cmp::Custom), Test::More ("is_deeply()"), Test::Deep, Test2::Tools::Compare. Others Scalar::Cmp which employs roughly the same rules as Data::Cmp but does not recurse into arrays/hashes and is meant to compare two scalar values. AUTHOR perlancar <perlancar@cpan.org> COPYRIGHT AND LICENSE This software is copyright (c) 2021, 2019, 2018 by perlancar@cpan.org. This is free software; you can redistribute it and/or modify it under the same terms as the Perl 5 programming language system itself.