+# -*- 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 = '1.15';
+our $VERSION = '1.57';
-# (feature name) => (internal name, used in %^H)
-my %feature = (
+our %feature = (
+ fc => 'feature_fc',
+ isa => 'feature_isa',
+ say => 'feature_say',
+ state => 'feature_state',
switch => 'feature_switch',
- say => "feature_say",
- state => "feature_state",
- unicode_strings => "feature_unicode",
+ bitwise => 'feature_bitwise',
+ evalbytes => 'feature_evalbytes',
+ signatures => 'feature_signatures',
+ current_sub => 'feature___SUB__',
+ refaliasing => 'feature_refaliasing',
+ postderef_qq => 'feature_postderef_qq',
+ unicode_eval => 'feature_unieval',
+ declared_refs => 'feature_myref',
+ unicode_strings => 'feature_unicode',
+);
+
+our %feature_bundle = (
+ "5.10" => [qw(say state switch)],
+ "5.11" => [qw(say state switch unicode_strings)],
+ "5.15" => [qw(current_sub evalbytes fc say state switch unicode_eval unicode_strings)],
+ "5.23" => [qw(current_sub evalbytes fc postderef_qq say state switch unicode_eval unicode_strings)],
+ "5.27" => [qw(bitwise current_sub evalbytes fc postderef_qq say state switch unicode_eval unicode_strings)],
+ "all" => [qw(bitwise current_sub declared_refs evalbytes fc isa postderef_qq refaliasing say signatures state switch unicode_eval unicode_strings)],
+ "default" => [qw()],
+);
+
+$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{"5.25"} = $feature_bundle{"5.23"};
+$feature_bundle{"5.26"} = $feature_bundle{"5.23"};
+$feature_bundle{"5.28"} = $feature_bundle{"5.27"};
+$feature_bundle{"5.29"} = $feature_bundle{"5.27"};
+$feature_bundle{"5.30"} = $feature_bundle{"5.27"};
+$feature_bundle{"5.31"} = $feature_bundle{"5.27"};
+$feature_bundle{"5.32"} = $feature_bundle{"5.27"};
+$feature_bundle{"5.9.5"} = $feature_bundle{"5.10"};
+my %noops = (
+ postderef => 1,
+ lexical_subs => 1,
);
+my %removed = (
+ array_base => 1,
+);
+
+our $hint_shift = 26;
+our $hint_mask = 0x1c000000;
+our @hint_bundles = qw( default 5.10 5.11 5.15 5.23 5.27 );
# 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 $hint_uni8bit = 0x00000800;
-# NB. the latest bundle must be loaded by the -E switch (see toke.c)
-
-my %feature_bundle = (
- "5.10" => [qw(switch say state)],
- "5.11" => [qw(switch say state unicode_strings)],
-);
-
-# special case
-$feature_bundle{"5.9.5"} = $feature_bundle{"5.10"};
-
# TODO:
# - think about versioned features (use feature switch => 2)
=head1 SYNOPSIS
- use feature qw(switch say);
+ use feature qw(say switch);
given ($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.
+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'>.
-=head2 The 'switch' feature
-
-C<use feature 'switch'> tells the compiler to enable the Perl 6
-given/when construct.
-
-See L<perlsyn/"Switch statements"> for details.
+=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.
-=head2 the 'unicode_strings' feature
+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.
+
+This feature is available starting with Perl 5.10.
+
+=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 does not change the internal representation of strings, but only how
+they are interpreted.
-C<use feature 'unicode_strings'> tells the compiler to treat
-all strings outside of C<use locale> and C<use bytes> as Unicode. It is
-available starting with Perl 5.11.3.
+C<no feature 'unicode_strings'> tells the compiler to use the traditional
+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.
-See L<perlunicode/The "Unicode Bug"> for details.
+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>;
+was extended further in Perl 5.26 to cover L<the range
+operator|perlop/Range Operators>; and was extended again in Perl 5.28 to
+cover L<special-cased whitespace splitting|perlfunc/split>.
+
+=head2 The 'unicode_eval' and 'evalbytes' features
+
+Together, these two features are intended to replace the legacy string
+C<eval> function, which behaves problematically in some instances. They are
+available starting with Perl 5.16, and are enabled by default by a
+S<C<use 5.16>> or higher declaration.
+
+C<unicode_eval> changes the behavior of plain string C<eval> to work more
+consistently, especially in the Unicode world. Certain (mis)behaviors
+couldn't be changed without breaking some things that had come to rely on
+them, so the feature can be enabled and disabled. Details are at
+L<perlfunc/Under the "unicode_eval" feature>.
+
+C<evalbytes> is like string C<eval>, but operating on a byte stream that is
+not UTF-8 encoded. Details are at L<perlfunc/evalbytes EXPR>. Without a
+S<C<use feature 'evalbytes'>> nor a S<C<use v5.16>> (or higher) declaration in
+the current scope, you can still access it by instead writing
+C<CORE::evalbytes>.
+
+=head2 The 'current_sub' feature
+
+This provides the C<__SUB__> token that returns a reference to the current
+subroutine or C<undef> outside of a subroutine.
+
+This feature is available starting with Perl 5.16.
+
+=head2 The 'array_base' feature
+
+This feature supported the legacy C<$[> variable. See L<perlvar/$[>.
+It was on by default but disabled under C<use v5.16> (see
+L</IMPLICIT LOADING>, below) and unavailable since perl 5.30.
+
+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
+
+In Perl versions prior to 5.26, this feature enabled
+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. From Perl 5.18 to 5.24,
+it was classed as experimental, and Perl emitted a warning for its
+usage, except when explicitly disabled:
+
+ no warnings "experimental::lexical_subs";
+
+As of Perl 5.26, use of this feature no longer triggers a warning, though
+the C<experimental::lexical_subs> warning category still exists (for
+compatibility with code that disables it). In addition, 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 '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
+
+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. Starting in Perl 5.28,
+C<use v5.28> will enable the feature. Before 5.28, it was still
+experimental and would emit a warning in the "experimental::bitwise"
+category.
+
+=head2 The 'declared_refs' 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::declared_refs";
+
+This allows a reference to a variable to be declared with C<my>, C<state>,
+our C<our>, or localized with C<local>. It is intended mainly for use in
+conjunction with the "refaliasing" feature. See L<perlref/Declaring a
+Reference to a Variable> for examples.
+
+This feature is available from Perl 5.26 onwards.
+
+=head2 The 'isa' feature
+
+This allows the use of the C<isa> infix operator, which tests whether the
+scalar given by the left operand is an object of the class given by the
+right operand. See L<perlop/Class Instance Operator> for more details.
+
+This feature is available from Perl 5.32 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 bundle is 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
+
+ :5.10 say state switch
+
+ :5.12 say state switch unicode_strings
+
+ :5.14 say state switch unicode_strings
+
+ :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
-Specifying sub-versions such as the C<0> in C<5.10.0> in feature bundles has
-no effect: feature bundles are guaranteed to be the same for all sub-versions.
+ :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
+
+ :5.26 say state switch unicode_strings
+ unicode_eval evalbytes current_sub fc
+ postderef_qq
+
+ :5.28 say state switch unicode_strings
+ unicode_eval evalbytes current_sub fc
+ postderef_qq bitwise
+
+ :5.30 say state switch unicode_strings
+ unicode_eval evalbytes current_sub fc
+ postderef_qq bitwise
+
+ :5.32 say state switch unicode_strings
+ unicode_eval evalbytes current_sub fc
+ postderef_qq bitwise
+
+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.
+
+ 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.
+
+Unlike C<use feature ":5.12">, saying C<use v5.12> (or any higher version)
+also does the equivalent of C<use strict>; see L<perlfunc/use> for details.
+
=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}) {
+ if (exists $noops{$name}) {
+ next;
+ }
+ if (!$import && exists $removed{$name}) {
+ next;
+ }
+ 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