manpagez: man pages & more
man stable(3)
Home | html | info | man
stable(3pm)            Perl Programmers Reference Guide            stable(3pm)



NAME

       stable - Experimental features made easy, once we know they're stable


VERSION

       version 0.031


SYNOPSIS

               use stable 'lexical_subs', 'bitwise';
               my sub is_odd($value) { $value & 1 }


DESCRIPTION

       The experimental pragma makes it easy to turn on experimental while
       turning off associated warnings.  You should read about it, if you
       don't already know what it does.

       Seeing "use experimental" in code might be scary.  In fact, it probably
       should be!  Code that uses experimental features might break in the
       future if the perl development team decides that the experiment needs
       to be altered.  When experiments become stable, because the developers
       decide they're a success, the warnings associated with them go away.
       When that happens, they can generally be turned on with "use feature".

       This is great, if you are using a version of perl where the feature you
       want is already stable.  If you're using an older perl, though, it
       might be the case that you want to use an experimental feature that
       still warns, even though there's no risk in using it, because
       subsequent versions of perl have that feature unchanged and now stable.

       Here's an example:  The "postderef" feature was added in perl 5.20.0.
       In perl 5.24.0, it was marked stable.  Using it would no longer trigger
       a warning.  The behavior of the feature didn't change between 5.20.0
       and 5.24.0.  That means that it's perfectly safe to use the feature on
       5.20 or 5.22, even though there's a warning.

       In that case, you could very justifiably add "use experimental
       'postderef'" but the casual reader may still be worried at seeing that.
       The "stable" pragma exists to turn on experimental features only when
       it's known that their behavior in the running perl is their stable
       behavior.

       If you try to use an experimental feature that isn't stable or
       available on the running version of perl, an exception will be thrown.
       You should also take care that you've required the version of "stable"
       that you need!

       If it's not immediately obvious why, here's a bit of explanation:

       o   "stable" comes with perl, starting with perl v5.38.

       o   Imagine that v5.38 adds a feature called "florps".  It will stop
           being experimental in v5.42.

       o   The version of "stable" that comes with perl v5.38 can't know that
           the florps experiment will succeed, so you can't "use stable
           'florps'" on the version of stable ships with v5.38, because it
           can't see the future!

       o   You'll need to write "use stable 1.234 'florps'" to say that you
           need version 1.234 of stable, which is when florps became known to
           stable.

       Sure, it's a little weird, but it's worth it!  The documentation of
       this pragma will tell you what version of "stable" you need to require
       in order to use various features.  See below.

       At present there are only a few "stable" features:

       o   "bitwise" - stable as of perl 5.22, available via stable 0.031

       o   "isa" - stable as of perl 5.32, available via stable 0.031

       o   "lexical_subs" - stable as of perl 5.22, available via stable 0.031

           Lexical subroutines were actually added in 5.18, and their design
           did not change, but significant bugs makes them unsafe to use
           before 5.22.

       o   "postderef" - stable as of perl 5.20, available via stable 0.031


SEE ALSO

       perlexperiment(1) contains more information about experimental
       features.


AUTHOR

       Leon Timmermans <leont@cpan.org>


COPYRIGHT AND LICENSE

       This software is copyright (c) 2013 by Leon Timmermans.

       This is free software; you can redistribute it and/or modify it under
       the same terms as the Perl 5 programming language system itself.

perl v5.38.2                      2023-11-28                       stable(3pm)

perl 5.38.2 - Generated Mon Dec 16 15:34:37 CST 2024
© manpagez.com 2000-2024
Individual documents may contain additional copyright information.