NAME
LV - LV ♥ lvalue
SYNOPSIS
use LV qw( lvalue get set );
my $xxx;
sub xxx :lvalue {
lvalue
get { $xxx }
set { $xxx = $_[0] }
}
xxx() = 42;
say xxx(); # says 42
DESCRIPTION
This module makes lvalue subroutines easy and practical to use. It's
inspired by the lvalue module which is sadly problematic because of the
existence of another module on CPAN called Lvalue. (They can get confused
on file-systems that have case-insensitive file names.)
LV comes with three different implementations, based on Variable::Magic,
Sentinel and `tie`; it will choose and use the best available one. You can
force LV to pick a particular implementation using:
$ENV{PERL_LV_IMPLEMENTATION} = 'Magic'; # or 'Sentinel' or 'Tie'
The tie implementation is the slowest, but will work on Perl 5.6 with only
core modules.
Functions
`lvalue(%args)`
Creates the magic lvalue. This must be the last expression evaluated
by the lvalue sub (and thus will be returned by the sub) but also must
not be returned using an explicit `return` keyword (which would break
its lvaluedness).
As a matter of style, you may like to omit the optional semicolon
after calling this function, which will act as a reminder that no
statement should follow this one.
The arguments are `get` and `set`, which each take a coderef:
sub xxx :lvalue {
lvalue(
get => sub { $xxx },
set => sub { $xxx = $_[0] },
); # semicolon
}
Note that the `set` coderef gets passed the rvalue part as $_[0].
`get { BLOCK }`, `set { BLOCK }`
Convenience functions for defining `get` and `set` arguments for
`lvalue`:
sub xxx :lvalue {
lvalue
get { $xxx }
set { $xxx = $_[0] }
}
As well as populating %args for `lvalue`, these functions also use
Sub::Name (if it's installed) to ensure that the anonymous coderefs
have sensible names for the purposes of stack traces, etc.
These functions are not exported by default.
`implementation()`
Can be used to determine the current backend.
Cannot be exported.
BUGS
Please report any bugs to <http://rt.cpan.org/Dist/Display.html?Queue=LV>.
SEE ALSO
lvalue, Sentinel.
AUTHOR
Toby Inkster <tobyink@cpan.org>.
COPYRIGHT AND LICENCE
This software is copyright (c) 2013 by Toby Inkster.
This is free software; you can redistribute it and/or modify it under the
same terms as the Perl 5 programming language system itself.
DISCLAIMER OF WARRANTIES
THIS PACKAGE IS PROVIDED "AS IS" AND WITHOUT ANY EXPRESS OR IMPLIED
WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED WARRANTIES OF
MERCHANTIBILITY AND FITNESS FOR A PARTICULAR PURPOSE.