NAME
Scalar::Defer - Calculate values on demand
SYNOPSIS
use Scalar::Defer; # exports 'defer' and 'lazy'
my ($x, $y);
my $dv = defer { ++$x }; # a defer-value (not memoized)
my $lv = lazy { ++$y }; # a lazy-value (memoized)
print "$dv $dv $dv"; # 1 2 3
print "$lv $lv $lv"; # 1 1 1
DESCRIPTION
This module exports two functions, "defer" and "lazy", for building
values that are evaluated on demand.
defer {...}
Takes a block or a code reference, and returns an overloaded value. Each
time that value is demanded, the block is evaluated again to yield a
fresh result.
lazy {...}
Like "defer", except the value is computed at most once. Subsequent
evaluation will simply use the cached result.
NOTES
Unlike the "tie"-based Data::Lazy, this module operates on *values*, not
*variables*. Therefore, assigning into $dv and $lv above will simply
replace the value, instead of triggering a "STORE" method call.
Also, thanks to the "overload"-based implementation, this module is
about 2x faster than Data::Lazy.
AUTHORS
Audrey Tang <
[email protected]>
COPYRIGHT (The "MIT" License)
Copyright 2006 by Audrey Tang <
[email protected]>.
Permission is hereby granted, free of charge, to any person obtaining a
copy of this software and associated documentation files (the
"Software"), to deal in the Software without restriction, including
without limitation the rights to use, copy, modify, merge, publish,
distribute, sublicense, and/or sell copies of the Software, and to
permit persons to whom the Software is fur- nished to do so, subject to
the following conditions:
The above copyright notice and this permission notice shall be included
in all copies or substantial portions of the Software.
THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
MERCHANTABILITY, FIT- NESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
IN NO EVENT SHALL THE X CONSORTIUM BE LIABLE FOR ANY CLAIM, DAMAGES OR
OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE,
ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
OTHER DEALINGS IN THE SOFTWARE.
