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constant-our-0.02
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NAME

constant::our - Perl pragma to declare constants like our vars

VERSION

Version 0.02

SYNOPSIS

use constant::our { DEBUG => 1 }; use constant::our { DEBUG_SQL => 1, DEBUG_CACHE => 1, };

###################### package My::Cool::Tools; use constant::our qw(DEBUG DEBUG_SQL);

if(DEBUG) { warn "DEBUG: $debug_info"; if(DEBUG_SQL) { warn "DEBUG_SQL: $querty"; } }

# or DEBUG && warn "DEBUG: $debug_info"; DEBUG && DEBUG_SQL && warn "DEBUG_SQL: $querty";

# Environment $ export CONSTANT_OUR_DEBUG=1 $ perl -e'use constant::our qw(DEBUG); DEBUG && {warn "Running in debug mode"}'

DESCRIPTION

This pragma extends standard pragma 'constant'.

As you may know, when a constant is used in an expression, Perl replaces it with its value at compile time, and may then optimize the expression further.

You can inspect this behavior by yourself:

$ perl -MO=Deparse -e'use constant{DEBUG => 1}; warn "1"; if(DEBUG){warn "2"} warn 3;' use constant ({'DEBUG', 1}); warn '1'; do { warn '2' }; warn 3;

All warns are here.

$ perl -MO=Deparse -e'use constant{DEBUG => 0}; warn "1"; if(DEBUG){warn "2"} warn 3;' use constant ({'DEBUG', 0}); warn '1'; '???'; warn 3;

Notice the '???' instead of the second 'warn'. So you can do something like this:

# in the main script use constant DEBUG => 0;

# in a module if(main::DEBUG) { # some debug code goes here }

But you should declare all constants you use, you can't simply write

if (main::DEBUG_SQL) { }

without corresponding

use constant DEBUG_SQL => 0;

in the main script.

With constant::our you can freely use "undeclared" constants in your condition statements.

# main script use constant::our { DEBUG => 1, DEBUG_CACHE => 1, };

###################### package My::Cool::Tools; use constant::our qw(DEBUG DEBUG_SQL); # don't need DEBUG_CACHE, but want (undeclared) DEBUG_SQL

DEBUG && warn "DEBUG: $debug_info"; # DEBUG --> 1 DEBUG && DEBUG_SQL && warn "DEBUG_SQL: $query"; # DEBUG_SQL --> undef

stderr: "DEBUG: ..."

IMPORTANT

A constant should be declared no more than one time. If you try to declare a constant twice (with different values), your program will die.

Since use of undeclared constant implicitly declares it, you should declare your constants _before_ you start use them.

EXPORT

Nothing by default.

SEE ALSO

constant

constant::abs && constant::def

THANKS

Bolshakova Elena Neil Bowers

AUTHOR

Green, <Evdokimov.Denis at gmail.com>

BUGS

Please report any bugs or feature requests to bug-constant-our at rt.cpan.org, or through the web interface at http://rt.cpan.org/NoAuth/ReportBug.html?Queue=constant::our. I will be notified, and then you'll automatically be notified of progress on your bug as I make changes.

SUPPORT

You can find documentation for this module with the perldoc command.

perldoc constant::our

You can also look for information at:

COPYRIGHT & LICENSE

Copyright 2009 Green, all rights reserved.

This program is free software; you can redistribute it and/or modify it under the same terms as Perl itself.