Copyright 2009 Kevin Ryde

This file is part of constant-defer.

constant-defer is free software; you can redistribute it and/or
modify it under the terms of the GNU General Public License as
published by the Free Software Foundation; either version 3, or (at
your option) any later version.

constant-defer is distributed in the hope that it will be
useful, but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
General Public License for more details.

You should have received a copy of the GNU General Public License along
with constant-defer.  If not, see <http://www.gnu.org/licenses/>.



constant::defer makes subroutines similar to the builtin constant.pm,
but with the value calculation deferred until the sub is actually run.

    use constant::defer FOO => sub { calculate;
                                     return $something };

This is handy for big or slow things only needed sometimes, or where
at least the pain can be put off the point needed.

Lazy or deferred calculations can be hidden behind a scalar variable
too.  The choice between a sub and a variable is a matter of style or
personal preference.  Both ways have advantages, see the
constant::defer POD for some notes.

The constant-defer home page is

    http://user42.tuxfamily.org/constant-defer/index.html