NAME
Syntax::Keyword::Val - Provides a readonly variant of 'my' called 'val'
WARNING
While I do have serious intentions for this module in the future, it is
definitely a *toy* as written now. At this stage, it serves better as a
simple example of using Keyword::Simple.
DESCRIPTION
Simply use this module, then place the "val" keyword where you'd
normally use "my" for a read-only variant.
use Syntax::Keyword::Val;
val $foo = "bar";
$foo = 123; # ERROR
val $foo = {a => 123, b => 456};
$foo->{a} = 666; # ERROR
$foo->{xyz} = "xyzzy"; # ERROR
del $foo->{b}; # ERROR
The implementation uses Data::Lock, which itself uses the very fast
internal SV flag to enforce the read-only status, so there should be no
runtime penalty for using it.
BUGS
Bugs and missing features aplenty. To start, due to the hacky
implementation using Keyword::Simple (which is great, but quite
limited), the "val" keyword currently only works for standalone
declarations, i.e. statements that would normally begin with "my".
Statements like this will not work:
# Doesn't work, will generate a syntax error
open val $fh, '<', $filename;
Only scalars and references can be declared as "val". Attempting to
declare a list or hash as a val will make it a normal variable (and
issue a warning)
# Issues a warning (assuming 'use warnings' is in effect)
val @foo = qw(foo bar baz);
Finally, "val" only applies to the first variable in a group, and the
rest are read-write as normal.
# Issues a warning (assuming 'use warnings' is in effect)
val ($foo, $bar) = @baz;
AUTHOR
Chuck Adams <
[email protected]>
COPYRIGHT AND LICENSE
This software is copyright (c) 2013 by Chuck Adams
This is free software; you can redistribute it and/or modify it under
the same terms as the Perl 5 programming language system itself.
