X-Git-Url: https://perl5.git.perl.org/perl5.git/blobdiff_plain/47e9d84a3af211d9a80e0f7c8a7d6c3f3d9c9cbc..b6dbf1d39057ebab301f6e56d7c7ebcd44cefe8b:/lib/feature.pm diff --git a/lib/feature.pm b/lib/feature.pm index 78cb8fc..668b430 100644 --- a/lib/feature.pm +++ b/lib/feature.pm @@ -1,34 +1,75 @@ +# -*- 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 = '1.22'; +our $VERSION = '1.57'; -# (feature name) => (internal name, used in %^H) -my %feature = ( +our %feature = ( + fc => 'feature_fc', + isa => 'feature_isa', say => 'feature_say', state => 'feature_state', switch => 'feature_switch', + bitwise => 'feature_bitwise', + evalbytes => 'feature_evalbytes', + signatures => 'feature_signatures', + current_sub => 'feature___SUB__', + refaliasing => 'feature_refaliasing', + postderef_qq => 'feature_postderef_qq', + unicode_eval => 'feature_unieval', + declared_refs => 'feature_myref', unicode_strings => 'feature_unicode', ); +our %feature_bundle = ( + "5.10" => [qw(say state switch)], + "5.11" => [qw(say state switch unicode_strings)], + "5.15" => [qw(current_sub evalbytes fc say state switch unicode_eval unicode_strings)], + "5.23" => [qw(current_sub evalbytes fc postderef_qq say state switch unicode_eval unicode_strings)], + "5.27" => [qw(bitwise current_sub evalbytes fc postderef_qq say state switch unicode_eval unicode_strings)], + "all" => [qw(bitwise current_sub declared_refs evalbytes fc isa postderef_qq refaliasing say signatures state switch unicode_eval unicode_strings)], + "default" => [qw()], +); + +$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 $hint_uni8bit = 0x00000800; -# NB. the latest bundle must be loaded by the -E switch (see toke.c) - -my %feature_bundle = ( - "5.10" => [qw(say state switch)], - "5.11" => [qw(say state switch unicode_strings)], - "5.12" => [qw(say state switch unicode_strings)], - "5.13" => [qw(say state switch unicode_strings)], - "5.14" => [qw(say state switch unicode_strings)], - "5.15" => [qw(say state switch unicode_strings)], -); - -# special case -$feature_bundle{"5.9.5"} = $feature_bundle{"5.10"}; - # TODO: # - think about versioned features (use feature switch => 2) @@ -40,29 +81,31 @@ feature - Perl pragma to enable new features use feature qw(say switch); given ($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, 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 prefix provides access to all Perl keywords, regardless of this pragma.) =head2 Lexical effect Like other pragmas (C, for example), features have a lexical -effect. C will only make the feature "foo" available +effect. C will only make the feature "foo" available from that point to the end of the enclosing block. { @@ -73,7 +116,7 @@ from that point to the end of the enclosing block. =head2 C -Features can also be turned off by using C. This too +Features can also be turned off by using C. This too has lexical effect. use feature 'say'; @@ -84,93 +127,328 @@ has lexical effect. } say "Yet it is here."; -C with no features specified will turn off all features. +C with no features specified will reset to the default group. To +disable I features (an unusual request!) use C. + +=head1 AVAILABLE FEATURES =head2 The 'say' feature -C tells the compiler to enable the Perl 6 +C tells the compiler to enable the Perl 6 style C function. See L for details. -=head2 the 'state' feature +This feature is available starting with Perl 5.10. + +=head2 The 'state' feature C tells the compiler to enable C variables. See L for details. +This feature is available starting with Perl 5.10. + =head2 The 'switch' feature +B: Because the L is +experimental, Perl will warn when you use this feature, unless you have +explicitly disabled the warning: + + no warnings "experimental::smartmatch"; + C tells the compiler to enable the Perl 6 given/when construct. -See L for details. +See L for details. + +This feature is available starting with Perl 5.10. -=head2 the 'unicode_strings' feature +=head2 The 'unicode_strings' feature -C tells the compiler to use Unicode semantics +C 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 or C). 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 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 for details.) For this reason, if you are potentially using Unicode in your program, the C subpragma is B 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; +was extended further in Perl 5.26 to cover L; and was extended again in Perl 5.28 to +cover L. + +=head2 The 'unicode_eval' and 'evalbytes' features + +Together, these two features are intended to replace the legacy string +C function, which behaves problematically in some instances. They are +available starting with Perl 5.16, and are enabled by default by a +S> or higher declaration. + +C changes the behavior of plain string C 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. + +C is like string C, but operating on a byte stream that is +not UTF-8 encoded. Details are at L. Without a +S> nor a S> (or higher) declaration in +the current scope, you can still access it by instead writing +C. + +=head2 The 'current_sub' feature + +This provides the C<__SUB__> token that returns a reference to the current +subroutine or C 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. +It was on by default but disabled under C (see +L, 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 tells the compiler to enable the C function, +which implements Unicode casefolding. + +See L 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, C +and C syntax. See L 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 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 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 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 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: 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 for details. + +This feature is available from Perl 5.20 onwards. + +=head2 The 'refaliasing' feature + +B: 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 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 for details. + +This feature is available from Perl 5.22 onwards. Starting in Perl 5.28, +C 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: 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, C, +our C, or localized with C. It is intended mainly for use in +conjunction with the "refaliasing" feature. See L for examples. + +This feature is available from Perl 5.26 onwards. + +=head2 The 'isa' feature + +This allows the use of the C 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 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. 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 which is equivalent to C. +It's possible to load multiple features together, using +a I. 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 + + :5.20 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, and Perl 5.14 -provides none, C is equivalent to C. + :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 or C 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 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 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 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 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), you may prefer: @@ -179,79 +457,96 @@ But to avoid portability warnings (see L), 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, saying C (or any higher version) +also does the equivalent of C; see L 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 should disable *all* features + # A bare C 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 { @@ -260,3 +555,5 @@ sub croak { } 1; + +# ex: set ro: