Perl::Comparison - Runtime access to perl comparison operators

- NAME
- SYNOPSIS
- EXPORTS
- DEPENDENCIES
- DESCRIPTION

- Motivation
- Notes

- PUBLIC INTERFACE

- %COMPARISIONS
- compare
- sort_compare
- sort_keydepth

- PACKAGE INTERNALS

- _either_undef
- _both_undef

- AUTHORS
- COPYRIGHT

# NAME

Perl::Comparison - Runtime access to perl comparison operators

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# SYNOPSIS

      use Perl::Comparison qw(compare);
      print compare('eq', 'abc', 'xyz') ? "True\n" : "False\n";

      use Perl::Comparison qw(sort_compare);
      my @items = qw(The black cat climbed the green tree);
      sort { &sort_compare('cmp', $a, $b) } @items;

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# EXPORTS

Nothing exported by default

Exported upon request

  compare, sort_compare, sort_keydepth

:all

  compare, sort_compare, sort_keydepth

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# DEPENDENCIES

This module requires these other modules and libraries:

        Exporter

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# DESCRIPTION

Efficient routine to compare scalar values when the operator is variable. This is particularly useful for dynamic patterns, such as those read in from a configuration file, taken from an argument, or specified in a table somewhere.

## Motivation

Efficiency and security, invoking eval (as `eval` or `m//e`) is not an option.

In some situations, the logic is more important than the function. Just like when you would use `no warnings`. For this reason these routines simply return the logical answer when values are undefined.

Basic functionality which can be extended. Okay, it's just nice to have some sugar some times. Extending this package with your own comparison routines should be straight foward. A few that we have added are:

      mod       Modulo
      bw        Stringwise begins-with
      ew        Stringwise ends-with

## Notes

Because one cannot pass modifiers to the regular expression engine, the following extensions were added:

      =~i       Regular expression match, case insensitive
      !~i       Regular expression does not match, case insensitive
      eqic      Equal ignoring case
      neic      Not equal ignoring case

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# PUBLIC INTERFACE

## %COMPARISIONS

Comparison routines

  The key is the comparison operator. The value is the subroutine which is executed.

  If you wanted to define an operator named `opr`, you would:

        Perl::Comparison::COMPARISONS{'opr'} = sub {
          # your code here
        };

  Your comparison is invoked by:

        compare('opr', 'a', 'b');

  And your subroutine will be passed `'a'` and `'b'`. In fact, all arguments are passed, allowing you to write tertiary comparisons, such as:

        compare('opr', 'a', 'b', 'c');

## compare

Wrapper for Perl's internal comparison operators.

  Support runtime comparison when the operator is held as a scalar.

  Where `$comparator` may be one of:

        &&        $a and $b are true vlaues
        ||        $a or $b is a true value
        eq        Stringwise equal
        ne        Stringwise not equal
        lt        Stringwise less than
        le        Stringwise less than or equal
        gt        Stringwise greater than
        ge        Stringwise greater than or equal
        =~        Regular expression match
        !~        Regular expression does not match
        cmp       Stringwise less-than, equal-to, or greater-than
        leg       Alias for cmp (see Perl 6)
        ==        Numeric equal
        !=        Numeric not equal
        <         Numeric less than
        >         Numeric greater than
        <=        Numeric less than or equal
        >=        Numeric greater than or equal
        <=>       Numeric less-than, equal-to, or greater-than

        =~i       Regular expression match, case insensitive
        !~i       Regular expression does not match, case insensitive
        eqic      Equal ignoring case
        neic      Not equal ignoring case
        mod       Modulo
        bw        Stringwise begins-with
        ew        Stringwise ends-with

  This example will return false:

        compare('eq','',undef);

  This example will return true:

        compare('eq','abc','abc');

  This example will return true:

        compare('ne','abc','Abc');

  This example will return false:

        compare('eq','abc',undef);

  This example will return true:

        compare('!~','abc','A');

  This example will return true:

        compare('=~','abc','a');

  This example will return true:

        compare('==',1234,1234);

  This example will return true:

        compare('>=',1234,1234);

  This example will return true:

        compare('eqic','abc','Abc');

  This example will return true:

        compare('==',undef,undef);

  This example will return false:

        compare('==',0,undef);

  This example will return false:

        compare('!~i','abc','A');

  This example will return true:

        compare('=~i','abc','A');

  This example will return true:

        compare('eqic','abc','Abc');

  This example will return false:

        compare('neic','abc','Abc');

  This example will return true:

        compare('mod',4,2);

  This example will return true:

        compare('bw','abc','a');

  This example will return false:

        compare('bw','abc','b');

  This example will return false:

        compare('ew','abc','b');

  This example will return true:

        compare('ew','abc','c');

## sort_compare

Compare for sorting, returning 1, 0 or -1

  See also compare

  This example:

        my @numbers = ( 20, 1, 10, 2 );
        join ';', sort { &sort_compare('<=>',$a,$b) } @numbers;

  will return:

        1;2;10;20

## sort_keydepth

Sort by the number of nodes in the key

  The key is the solodus (/) character.

  This example will not abort:

        use Perl::Comparison qw(sort_keydepth);

  This example:

        # The deepest elements come last
        join ';', sort {&sort_keydepth($a, $b)} qw(t/w/o o/ne th/r/e/e);

  will return:

        o/ne;t/w/o;th/r/e/e

  This example:

        # Those without come after undefined but before those with
        no warnings 'uninitialized';
        join ';', sort {&sort_keydepth($a, $b)} (qw(t/w/o o/ne none th/r/e/e), undef);

  will return:

        ;none;o/ne;t/w/o;th/r/e/e

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# PACKAGE INTERNALS

## _either_undef

Are either operands undefined?

## _both_undef

Are both operands undefined?

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# AUTHORS

        Ryan Gies <ryangies@cpan.org>

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# COPYRIGHT

        Copyright (C) 2014-2016 by Ryan Gies. All rights reserved.
        Copyright (C) 2006-2013 by Livesite Networks, LLC. All rights reserved.
        Copyright (C) 2000-2005 by Ryan Gies. All rights reserved.
        Redistribution and use in source and binary forms, with or without
        modification, are permitted provided that the following conditions are met:
        * Redistributions of source code must retain the above copyright notice,
        this list of conditions and the following disclaimer.
        * The origin of this software must not be misrepresented; you must not
        claim that you wrote the original software. If you use this software in a
        product, an acknowledgment in the product documentation would be
        appreciated but is not required.
        * Altered source versions must be plainly marked as such, and must not be
        misrepresented as being the original software.
        * The name of the author may not be used to endorse or promote products
        derived from this software without specific prior written permission.

        THIS SOFTWARE IS PROVIDED BY THE AUTHOR "AS IS" AND ANY EXPRESS OR IMPLIED
        WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
        MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO
        EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
        EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT
        OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
        INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
        CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING
        IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY
        OF SUCH DAMAGE.
        To the best of our knowledge, no patented algorithms have been used. However, we
        do not have the resources to carry out a patent search, and therefore cannot
        give any guarantee of the above statement.

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