gimp::feature(3) [redhat man page]
Feature(3) User Contributed Perl Documentation Feature(3) NAME
Gimp::Feature - check for specific features to be present before registering the script. SYNOPSIS
use Gimp::Feature; or use Gimp::Feature qw(feature1 feature2 ...); DESCRIPTION
This module can be used to check for specific features to be present. This can be used to deny running the script when neccessary features are not present. While some features can be checked for at any time, the Gimp::Fu module offers a nicer way to check for them. "gtk" checks for the presence of the gtk interface module. "gtk-1.1", "gtk-1.2" checks for the presence of gtk-1.1 (1.2) or higher. "perl-5.005" checks for perl version 5.005 or higher. "pdl" checks for the presence of a suitable version of PDL (>=1.9906). "gnome" checks for the presence of the Gnome-Perl module. "gtkxmhtl" checks for the presence of the Gtk::XmHTML module. "unix" checks wether the script runs on a unix-like operating system. At the moment, this is every system except windows, macos, os2 and vms. "persistency" checks wether the "Gimp::Data" module (Gimp::Data) can handle complex persistent data structures, i.e. perl references in addition to plain strings. The following features can only be checked after "Gimp-"main> has been called (usually found in the form "exit main"). See Gimp::Fu on how to check for these. "gimp-1.1", "gimp-1.2" checks for the presense of gimp in at least version 1.1 (1.2). FUNCTIONS present(feature) Checks for the presense of the single feature given as the argument. Returns true if the feature is present, false otherwise. need(feature,[function-name]) Require a specific feature. If the required feature is not present the program will exit gracefully, logging an appropriate message. You can optionally supply a function name to further specify the place where this feature was missing. This is the function used when importing symbols from the module. missing(feature-description,[function-name]) Indicates that a generic feature (described by the first argument) is missing. A function name can further be specified. This function will log the given message and exit gracefully. describe(feature) Returns a string describing the given feature in more detail, or undef if there is no description for this feature. list() Returns a list of features that can be checked for. This list might not be complete. AUTHOR
Marc Lehmann <pcg@goof.com> SEE ALSO
perl(1), Gimp(1). perl v5.8.0 1999-11-22 Feature(3)
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feature(3pm) Perl Programmers Reference Guide feature(3pm) NAME
feature - Perl pragma to enable new features SYNOPSIS
use feature qw(switch say); given ($foo) { when(1) { say "$foo == 1" } when ([2,3]) { say "$foo == 2 || $foo == 3" } when (/^a[bc]d$/) { say "$foo eq 'abd' || $foo eq 'acd'" } when ($_ > 100) { say "$foo > 100" } default { say "None of the above" } } use feature ':5.10'; # loads all features available in perl 5.10 DESCRIPTION
It is usually impossible to add new syntax to Perl without breaking some existing programs. This pragma provides a way to minimize that risk. New syntactic constructs, or new semantic meanings to older constructs, can be enabled by "use feature 'foo'", and will be parsed only when the appropriate feature pragma is in scope. Lexical effect Like other pragmas ("use strict", for example), features have a lexical effect. "use feature qw(foo)" will only make the feature "foo" available from that point to the end of the enclosing block. { use feature 'say'; say "say is available here"; } print "But not here. "; "no feature" Features can also be turned off by using "no feature "foo"". This too has lexical effect. use feature 'say'; say "say is available here"; { no feature 'say'; print "But not here. "; } say "Yet it is here."; "no feature" with no features specified will turn off all features. The 'switch' feature "use feature 'switch'" tells the compiler to enable the Perl 6 given/when construct. See "Switch statements" in perlsyn for details. The 'say' feature "use feature 'say'" tells the compiler to enable the Perl 6 "say" function. See "say" in perlfunc for details. the 'state' feature "use feature 'state'" tells the compiler to enable "state" variables. See "Persistent Private Variables" in perlsub for details. the 'unicode_strings' feature "use feature 'unicode_strings'" tells the compiler to treat all strings outside of "use locale" and "use bytes" as Unicode. It is available starting with Perl 5.11.3. See "The "Unicode Bug"" in perlunicode for details. FEATURE BUNDLES
It's possible to load a whole slew of features in one go, using a feature bundle. The name of a feature bundle is prefixed with a colon, to distinguish it from an actual feature. At present, the only feature bundle is "use feature ":5.10"" which is equivalent to "use feature qw(switch say state)". Specifying sub-versions such as the 0 in 5.10.0 in feature bundles has no effect: feature bundles are guaranteed to be the same for all sub-versions. IMPLICIT LOADING
There are two ways to load the "feature" pragma implicitly : o By using the "-E" switch on the command-line instead of "-e". It enables all available features in the main compilation unit (that is, the one-liner.) o By requiring explicitly a minimal Perl version number for your program, with the "use VERSION" construct, and when the version is higher than or equal to 5.10.0. That is, use 5.10.0; will do an implicit use feature ':5.10'; and so on. Note how the trailing sub-version is automatically stripped from the version. But to avoid portability warnings (see "use" in perlfunc), you may prefer: use 5.010; with the same effect. perl v5.12.1 2010-05-13 feature(3pm)