NAME

Perl::Compare - Runtime access to perl comparison operators

SYNOPSIS

  use Perl::Compare qw(compare);
  print compare('eq', 'abc', 'xyz') ? "True\n" : "False\n";
    
  use Perl::Compare qw(sort_compare);
  my @items = qw(The black cat climbed the green tree);
  sort { &sort_compare('cmp', $a, $b) } @items;

EXPORTS

Nothing exported by default

Exported upon request

compare, sort_compare, sort_keydepth

:all

compare, sort_compare, sort_keydepth

DEPENDENCIES

This module requires these other modules and libraries:

    Exporter

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

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::Compare::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::Compare 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

PACKAGE INTERNALS

_either_undef

Are either operands undefined?

_both_undef

Are both operands undefined?

AUTHORS

    Ryan Gies <ryangies@cpan.org>

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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