+# -*- buffer-read-only: t -*-
+# !!!!!!! DO NOT EDIT THIS FILE !!!!!!!
+# This file is built by regen/feature.pl.
+# Any changes made here will be lost!
+
package feature;
-our $VERSION = '1.24';
+our $VERSION = '1.42';
-# (feature name) => (internal name, used in %^H)
-my %feature = (
+our %feature = (
+ fc => 'feature_fc',
say => 'feature_say',
state => 'feature_state',
switch => 'feature_switch',
+ bitwise => 'feature_bitwise',
evalbytes => 'feature_evalbytes',
+ postderef => 'feature_postderef',
+ array_base => 'feature_arybase',
+ signatures => 'feature_signatures',
current_sub => 'feature___SUB__',
+ refaliasing => 'feature_refaliasing',
+ lexical_subs => 'feature_lexsubs',
+ postderef_qq => 'feature_postderef_qq',
unicode_eval => 'feature_unieval',
unicode_strings => 'feature_unicode',
);
-# This gets set (for now) in $^H as well as in %^H,
-# for runtime speed of the uc/lc/ucfirst/lcfirst functions.
-# See HINT_UNI_8_BIT in perl.h.
-our $hint_uni8bit = 0x00000800;
-
-# NB. the latest bundle must be loaded by the -E switch (see toke.c)
-
our %feature_bundle = (
- "default" => [],
- "5.10" => [qw(say state switch)],
- "5.11" => [qw(say state switch unicode_strings)],
- "5.15" => [qw(say state switch unicode_strings unicode_eval
- evalbytes current_sub)],
+ "5.10" => [qw(array_base say state switch)],
+ "5.11" => [qw(array_base say state switch unicode_strings)],
+ "5.15" => [qw(current_sub evalbytes fc say state switch unicode_eval unicode_strings)],
+ "5.23" => [qw(current_sub evalbytes fc postderef_qq say state switch unicode_eval unicode_strings)],
+ "all" => [qw(array_base bitwise current_sub evalbytes fc lexical_subs postderef postderef_qq refaliasing say signatures state switch unicode_eval unicode_strings)],
+ "default" => [qw(array_base)],
);
-# Each of these is the same as the previous bundle
-for(12...14, 16) {
- $feature_bundle{"5.$_"} = $feature_bundle{"5.".($_-1)}
-}
-
-# special case
+$feature_bundle{"5.12"} = $feature_bundle{"5.11"};
+$feature_bundle{"5.13"} = $feature_bundle{"5.11"};
+$feature_bundle{"5.14"} = $feature_bundle{"5.11"};
+$feature_bundle{"5.16"} = $feature_bundle{"5.15"};
+$feature_bundle{"5.17"} = $feature_bundle{"5.15"};
+$feature_bundle{"5.18"} = $feature_bundle{"5.15"};
+$feature_bundle{"5.19"} = $feature_bundle{"5.15"};
+$feature_bundle{"5.20"} = $feature_bundle{"5.15"};
+$feature_bundle{"5.21"} = $feature_bundle{"5.15"};
+$feature_bundle{"5.22"} = $feature_bundle{"5.15"};
+$feature_bundle{"5.24"} = $feature_bundle{"5.23"};
$feature_bundle{"5.9.5"} = $feature_bundle{"5.10"};
+our $hint_shift = 26;
+our $hint_mask = 0x1c000000;
+our @hint_bundles = qw( default 5.10 5.11 5.15 5.23 );
+
+# This gets set (for now) in $^H as well as in %^H,
+# for runtime speed of the uc/lc/ucfirst/lcfirst functions.
+# See HINT_UNI_8_BIT in perl.h.
+our $hint_uni8bit = 0x00000800;
+
# TODO:
# - think about versioned features (use feature switch => 2)
use feature qw(say switch);
given ($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" }
+ 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
+ use v5.10; # implicitly loads :5.10 feature bundle
+
=head1 DESCRIPTION
It is usually impossible to add new syntax to Perl without breaking
-some existing programs. This pragma provides a way to minimize that
+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 C<use feature 'foo'>, and will be parsed
-only when the appropriate feature pragma is in scope. (Nevertheless, the
+only when the appropriate feature pragma is in scope. (Nevertheless, the
C<CORE::> prefix provides access to all Perl keywords, regardless of this
pragma.)
=head2 Lexical effect
Like other pragmas (C<use strict>, for example), features have a lexical
-effect. C<use feature qw(foo)> will only make the feature "foo" available
+effect. C<use feature qw(foo)> will only make the feature "foo" available
from that point to the end of the enclosing block.
{
=head2 C<no feature>
-Features can also be turned off by using C<no feature "foo">. This too
+Features can also be turned off by using C<no feature "foo">. This too
has lexical effect.
use feature 'say';
}
say "Yet it is here.";
-C<no feature> with no features specified will turn off all features.
+C<no feature> with no features specified will reset to the default group. To
+disable I<all> features (an unusual request!) use C<no feature ':all'>.
+
+=head1 AVAILABLE FEATURES
=head2 The 'say' feature
-C<use feature 'say'> tells the compiler to enable the Perl 6
+C<use feature 'say'> tells the compiler to enable the Perl 6 style
C<say> function.
See L<perlfunc/say> for details.
-=head2 the 'state' feature
+This feature is available starting with Perl 5.10.
+
+=head2 The 'state' feature
C<use feature 'state'> tells the compiler to enable C<state>
variables.
See L<perlsub/"Persistent Private Variables"> for details.
+This feature is available starting with Perl 5.10.
+
=head2 The 'switch' feature
+B<WARNING>: Because the L<smartmatch operator|perlop/"Smartmatch Operator"> is
+experimental, Perl will warn when you use this feature, unless you have
+explicitly disabled the warning:
+
+ no warnings "experimental::smartmatch";
+
C<use feature 'switch'> tells the compiler to enable the Perl 6
given/when construct.
-See L<perlsyn/"Switch statements"> for details.
+See L<perlsyn/"Switch Statements"> for details.
-=head2 the 'unicode_strings' feature
+This feature is available starting with Perl 5.10.
-C<use feature 'unicode_strings'> tells the compiler to use Unicode semantics
+=head2 The 'unicode_strings' feature
+
+C<use feature 'unicode_strings'> tells the compiler to use Unicode rules
in all string operations executed within its scope (unless they are also
within the scope of either C<use locale> or C<use bytes>). The same applies
to all regular expressions compiled within the scope, even if executed outside
-it.
+it. It does not change the internal representation of strings, but only how
+they are interpreted.
C<no feature 'unicode_strings'> tells the compiler to use the traditional
-Perl semantics wherein the native character set semantics is used unless it is
+Perl rules wherein the native character set rules is used unless it is
clear to Perl that Unicode is desired. This can lead to some surprises
when the behavior suddenly changes. (See
L<perlunicode/The "Unicode Bug"> for details.) For this reason, if you are
potentially using Unicode in your program, the
C<use feature 'unicode_strings'> subpragma is B<strongly> recommended.
-This subpragma is available starting with Perl 5.11.3, but was not fully
-implemented until 5.13.8.
+This feature is available starting with Perl 5.12; was almost fully
+implemented in Perl 5.14; and extended in Perl 5.16 to cover C<quotemeta>.
-=head2 the 'unicode_eval' and 'evalbytes' features
+=head2 The 'unicode_eval' and 'evalbytes' features
Under the C<unicode_eval> feature, Perl's C<eval> function, when passed a
string, will evaluate it as a string of characters, ignoring any
This feature is available starting with Perl 5.16.
+=head2 The 'array_base' feature
+
+This feature supports the legacy C<$[> variable. See L<perlvar/$[> and
+L<arybase>. It is on by default but disabled under C<use v5.16> (see
+L</IMPLICIT LOADING>, below).
+
+This feature is available under this name starting with Perl 5.16. In
+previous versions, it was simply on all the time, and this pragma knew
+nothing about it.
+
+=head2 The 'fc' feature
+
+C<use feature 'fc'> tells the compiler to enable the C<fc> function,
+which implements Unicode casefolding.
+
+See L<perlfunc/fc> for details.
+
+This feature is available from Perl 5.16 onwards.
+
+=head2 The 'lexical_subs' feature
+
+B<WARNING>: This feature is still experimental and the implementation may
+change in future versions of Perl. For this reason, Perl will
+warn when you use the feature, unless you have explicitly disabled the
+warning:
+
+ no warnings "experimental::lexical_subs";
+
+This enables declaration of subroutines via C<my sub foo>, C<state sub foo>
+and C<our sub foo> syntax. See L<perlsub/Lexical Subroutines> for details.
+
+This feature is available from Perl 5.18 onwards.
+
+=head2 The 'postderef' and 'postderef_qq' features
+
+The 'postderef_qq' feature extends the applicability of L<postfix
+dereference syntax|perlref/Postfix Dereference Syntax> so that postfix array
+and scalar dereference are available in double-quotish interpolations. For
+example, it makes the following two statements equivalent:
+
+ my $s = "[@{ $h->{a} }]";
+ my $s = "[$h->{a}->@*]";
+
+This feature is available from Perl 5.20 onwards. In Perl 5.20 and 5.22, it
+was classed as experimental, and Perl emitted a warning for its
+usage, except when explicitly disabled:
+
+ no warnings "experimental::postderef";
+
+As of Perl 5.24, use of this feature no longer triggers a warning, though
+the C<experimental::postderef> warning category still exists (for
+compatibility with code that disables it).
+
+The 'postderef' feature was used in Perl 5.20 and Perl 5.22 to enable
+postfix dereference syntax outside double-quotish interpolations. In those
+versions, using it triggered the C<experimental::postderef> warning in the
+same way as the 'postderef_qq' feature did. As of Perl 5.24, this syntax is
+not only no longer experimental, but it is enabled for all Perl code,
+regardless of what feature declarations are in scope.
+
+=head2 The 'signatures' feature
+
+B<WARNING>: This feature is still experimental and the implementation may
+change in future versions of Perl. For this reason, Perl will
+warn when you use the feature, unless you have explicitly disabled the
+warning:
+
+ no warnings "experimental::signatures";
+
+This enables unpacking of subroutine arguments into lexical variables
+by syntax such as
+
+ sub foo ($left, $right) {
+ return $left + $right;
+ }
+
+See L<perlsub/Signatures> for details.
+
+This feature is available from Perl 5.20 onwards.
+
+=head2 The 'refaliasing' feature
+
+B<WARNING>: This feature is still experimental and the implementation may
+change in future versions of Perl. For this reason, Perl will
+warn when you use the feature, unless you have explicitly disabled the
+warning:
+
+ no warnings "experimental::refaliasing";
+
+This enables aliasing via assignment to references:
+
+ \$a = \$b; # $a and $b now point to the same scalar
+ \@a = \@b; # to the same array
+ \%a = \%b;
+ \&a = \&b;
+ foreach \%hash (@array_of_hash_refs) {
+ ...
+ }
+
+See L<perlref/Assigning to References> for details.
+
+This feature is available from Perl 5.22 onwards.
+
+=head2 The 'bitwise' feature
+
+B<WARNING>: This feature is still experimental and the implementation may
+change in future versions of Perl. For this reason, Perl will
+warn when you use the feature, unless you have explicitly disabled the
+warning:
+
+ no warnings "experimental::bitwise";
+
+This makes the four standard bitwise operators (C<& | ^ ~>) treat their
+operands consistently as numbers, and introduces four new dotted operators
+(C<&. |. ^. ~.>) that treat their operands consistently as strings. The
+same applies to the assignment variants (C<&= |= ^= &.= |.= ^.=>).
+
+See L<perlop/Bitwise String Operators> for details.
+
+This feature is available from Perl 5.22 onwards.
+
=head1 FEATURE BUNDLES
-It's possible to load a whole slew of features in one go, using
-a I<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 bundles correspond to Perl releases, e.g. C<use feature
-":5.10"> which is equivalent to C<use feature qw(switch say state)>.
+It's possible to load multiple features together, using
+a I<feature bundle>. The name of a feature bundle is prefixed with
+a colon, to distinguish it from an actual feature.
+
+ use feature ":5.10";
+
+The following feature bundles are available:
+
+ bundle features included
+ --------- -----------------
+ :default array_base
+
+ :5.10 say state switch array_base
+
+ :5.12 say state switch unicode_strings array_base
+
+ :5.14 say state switch unicode_strings array_base
+
+ :5.16 say state switch unicode_strings
+ unicode_eval evalbytes current_sub fc
+
+ :5.18 say state switch unicode_strings
+ unicode_eval evalbytes current_sub fc
-By convention, the feature bundle for any given Perl release includes
-the features of previous releases, down to and including 5.10, the
-first official release to provide this facility. Since Perl 5.12
-only provides one new feature, C<unicode_strings>, and Perl 5.14
-provides none, C<use feature ":5.14"> is equivalent to C<use feature
-qw(switch say state unicode_strings)>.
+ :5.20 say state switch unicode_strings
+ unicode_eval evalbytes current_sub fc
+
+ :5.22 say state switch unicode_strings
+ unicode_eval evalbytes current_sub fc
+
+ :5.24 say state switch unicode_strings
+ unicode_eval evalbytes current_sub fc
+ postderef_qq
+
+The C<:default> bundle represents the feature set that is enabled before
+any C<use feature> or C<no feature> declaration.
Specifying sub-versions such as the C<0> in C<5.14.0> in feature bundles has
-no effect: feature bundles are guaranteed to be the same for all sub-versions.
+no effect. Feature bundles are guaranteed to be the same for all sub-versions.
-Note that instead of using release-based feature bundles it is usually
-better, and shorter, to use implicit loading as described below.
+ use feature ":5.14.0"; # same as ":5.14"
+ use feature ":5.14.1"; # same as ":5.14"
=head1 IMPLICIT LOADING
-There are two ways to load the C<feature> pragma implicitly :
+Instead of loading feature bundles by name, it is easier to let Perl do
+implicit loading of a feature bundle for you.
+
+There are two ways to load the C<feature> pragma implicitly:
=over 4
=item *
-By using the C<-E> switch on the command-line instead of C<-e>. It enables
-all available features in the main compilation unit (that is, the one-liner.)
+By using the C<-E> switch on the Perl command-line instead of C<-e>.
+That will enable the feature bundle for that version of Perl in the
+main compilation unit (that is, the one-liner that follows C<-E>).
=item *
-By requiring explicitly a minimal Perl version number for your program, with
-the C<use VERSION> construct, and when the version is higher than or equal to
-5.10.0. That is,
+By explicitly requiring a minimum Perl version number for your program, with
+the C<use VERSION> construct. That is,
- use 5.10.0;
+ use v5.10.0;
will do an implicit
+ no feature ':all';
use feature ':5.10';
-and so on. Note how the trailing sub-version is automatically stripped from the
+and so on. Note how the trailing sub-version
+is automatically stripped from the
version.
But to avoid portability warnings (see L<perlfunc/use>), you may prefer:
with the same effect.
+If the required version is older than Perl 5.10, the ":default" feature
+bundle is automatically loaded instead.
+
=back
=cut
sub import {
- my $class = shift;
- if (@_ == 0) {
- croak("No features specified");
- }
- while (@_) {
- my $name = shift(@_);
- if (substr($name, 0, 1) eq ":") {
- my $v = substr($name, 1);
- if (!exists $feature_bundle{$v}) {
- $v =~ s/^([0-9]+)\.([0-9]+).[0-9]+$/$1.$2/;
- if (!exists $feature_bundle{$v}) {
- unknown_feature_bundle(substr($name, 1));
- }
- }
- unshift @_, @{$feature_bundle{$v}};
- next;
- }
- if (!exists $feature{$name}) {
- unknown_feature($name);
- }
- $^H{$feature{$name}} = 1;
- $^H |= $hint_uni8bit if $name eq 'unicode_strings';
+ shift;
+
+ if (!@_) {
+ croak("No features specified");
}
+
+ __common(1, @_);
}
sub unimport {
- my $class = shift;
+ shift;
- # A bare C<no feature> should disable *all* features
+ # A bare C<no feature> should reset to the default bundle
if (!@_) {
- delete @^H{ values(%feature) };
- $^H &= ~ $hint_uni8bit;
+ $^H &= ~($hint_uni8bit|$hint_mask);
return;
}
- while (@_) {
- my $name = shift;
- if (substr($name, 0, 1) eq ":") {
- my $v = substr($name, 1);
- if (!exists $feature_bundle{$v}) {
- $v =~ s/^([0-9]+)\.([0-9]+).[0-9]+$/$1.$2/;
- if (!exists $feature_bundle{$v}) {
- unknown_feature_bundle(substr($name, 1));
- }
- }
- unshift @_, @{$feature_bundle{$v}};
- next;
- }
- if (!exists($feature{$name})) {
- unknown_feature($name);
+ __common(0, @_);
+}
+
+
+sub __common {
+ my $import = shift;
+ my $bundle_number = $^H & $hint_mask;
+ my $features = $bundle_number != $hint_mask
+ && $feature_bundle{$hint_bundles[$bundle_number >> $hint_shift]};
+ if ($features) {
+ # Features are enabled implicitly via bundle hints.
+ # Delete any keys that may be left over from last time.
+ delete @^H{ values(%feature) };
+ $^H |= $hint_mask;
+ for (@$features) {
+ $^H{$feature{$_}} = 1;
+ $^H |= $hint_uni8bit if $_ eq 'unicode_strings';
}
- else {
- delete $^H{$feature{$name}};
+ }
+ while (@_) {
+ my $name = shift;
+ if (substr($name, 0, 1) eq ":") {
+ my $v = substr($name, 1);
+ if (!exists $feature_bundle{$v}) {
+ $v =~ s/^([0-9]+)\.([0-9]+).[0-9]+$/$1.$2/;
+ if (!exists $feature_bundle{$v}) {
+ unknown_feature_bundle(substr($name, 1));
+ }
+ }
+ unshift @_, @{$feature_bundle{$v}};
+ next;
+ }
+ if (!exists $feature{$name}) {
+ unknown_feature($name);
+ }
+ if ($import) {
+ $^H{$feature{$name}} = 1;
+ $^H |= $hint_uni8bit if $name eq 'unicode_strings';
+ } else {
+ delete $^H{$feature{$name}};
$^H &= ~ $hint_uni8bit if $name eq 'unicode_strings';
- }
+ }
}
}
sub unknown_feature {
my $feature = shift;
croak(sprintf('Feature "%s" is not supported by Perl %vd',
- $feature, $^V));
+ $feature, $^V));
}
sub unknown_feature_bundle {
my $feature = shift;
croak(sprintf('Feature bundle "%s" is not supported by Perl %vd',
- $feature, $^V));
+ $feature, $^V));
}
sub croak {
}
1;
+
+# ex: set ro:
https://perl5.git.perl.org / perl5.git / blobdiff