NAME

Lexical::SingleAssignment - Single assignment lexical variables

{
	# lexically scoped, like use strict
	use Lexical::SingleAssignment;


	# declare a lexical normally and give it a value
	my $x = "Foo";


	# compile time error, no initial value provided
	my $y;


	# compile time error, assignment after declaration
	$x = "bar";


	# runtime error, read only variable
	my $ref = \$x;
	$$ref = "bar";


	{
		no Lexical::SingleAssignment;


		# runtime error, $x is still readonly from parent scope
		$x = "bar";


		# no error, module not in enabled in this scope
		my $inner;
		$inner = 3;
	}
}

DESCRIPTION

This module implements lexically scoped single assignment lexicals.

When this module is in scope all lexical variables must be assigned a value at their declaration site, and cannot be modified afterwords.

In other words, when this module is in effect all lexicals must be assigned to exactly once, whereas normally you may assign zero or more times.

This is somewhat similar to immutable name bindings in other languages, but the SVs created are still copies (they are just readonly copies).

VERSION CONTROL

This module is maintained using git. You can get the latest version from git://github.com/nothingmuch/Lexical-SingleAssignment.git.

AUTHOR

Yuval Kogman <nothingmuch@woobling.org>

COPYRIGHT

Copyright (c) 2009 Yuval Kogman. All rights reserved
This program is free software; you can redistribute
it and/or modify it under the same terms as Perl itself.