Commit | Line | Data |
---|---|---|
69bcf1d3 FC |
1 | # -*- buffer-read-only: t -*- |
2 | # !!!!!!! DO NOT EDIT THIS FILE !!!!!!! | |
3 | # This file is built by regen/feature.pl. | |
4 | # Any changes made here will be lost! | |
5 | ||
0d863452 RH |
6 | package feature; |
7 | ||
d24d2f9e | 8 | our $VERSION = '1.38'; |
0d863452 | 9 | |
0bb01b05 | 10 | our %feature = ( |
2a4315f8 | 11 | fc => 'feature_fc', |
47e9d84a EB |
12 | say => 'feature_say', |
13 | state => 'feature_state', | |
1863b879 | 14 | switch => 'feature_switch', |
7d789282 | 15 | evalbytes => 'feature_evalbytes', |
b9a36c95 | 16 | postderef => 'feature_postderef', |
3fff3427 | 17 | array_base => 'feature_arybase', |
30d9c59b | 18 | signatures => 'feature_signatures', |
84ed0108 | 19 | current_sub => 'feature___SUB__', |
baabe3fb | 20 | refaliasing => 'feature_refaliasing', |
ebd25686 | 21 | lexical_subs => 'feature_lexsubs', |
158becca | 22 | postderef_qq => 'feature_postderef_qq', |
cda6b701 | 23 | unicode_eval => 'feature_unieval', |
47e9d84a | 24 | unicode_strings => 'feature_unicode', |
bc9b29db RH |
25 | ); |
26 | ||
0d2bd2aa | 27 | our %feature_bundle = ( |
69bcf1d3 FC |
28 | "5.10" => [qw(array_base say state switch)], |
29 | "5.11" => [qw(array_base say state switch unicode_strings)], | |
2a4315f8 | 30 | "5.15" => [qw(current_sub evalbytes fc say state switch unicode_eval unicode_strings)], |
baabe3fb | 31 | "all" => [qw(array_base current_sub evalbytes fc lexical_subs postderef postderef_qq refaliasing say signatures state switch unicode_eval unicode_strings)], |
69bcf1d3 | 32 | "default" => [qw(array_base)], |
0d863452 | 33 | ); |
d052521a | 34 | |
88da30d7 FC |
35 | $feature_bundle{"5.12"} = $feature_bundle{"5.11"}; |
36 | $feature_bundle{"5.13"} = $feature_bundle{"5.11"}; | |
37 | $feature_bundle{"5.14"} = $feature_bundle{"5.11"}; | |
38 | $feature_bundle{"5.16"} = $feature_bundle{"5.15"}; | |
d6402ebe | 39 | $feature_bundle{"5.17"} = $feature_bundle{"5.15"}; |
52fc5c56 | 40 | $feature_bundle{"5.18"} = $feature_bundle{"5.15"}; |
d09258e7 RS |
41 | $feature_bundle{"5.19"} = $feature_bundle{"5.15"}; |
42 | $feature_bundle{"5.20"} = $feature_bundle{"5.15"}; | |
b530a4ea RS |
43 | $feature_bundle{"5.21"} = $feature_bundle{"5.15"}; |
44 | $feature_bundle{"5.22"} = $feature_bundle{"5.15"}; | |
88da30d7 | 45 | $feature_bundle{"5.9.5"} = $feature_bundle{"5.10"}; |
69bcf1d3 | 46 | |
0bb01b05 FC |
47 | our $hint_shift = 26; |
48 | our $hint_mask = 0x1c000000; | |
49 | our @hint_bundles = qw( default 5.10 5.11 5.15 ); | |
ada44f8c | 50 | |
69bcf1d3 FC |
51 | # This gets set (for now) in $^H as well as in %^H, |
52 | # for runtime speed of the uc/lc/ucfirst/lcfirst functions. | |
53 | # See HINT_UNI_8_BIT in perl.h. | |
54 | our $hint_uni8bit = 0x00000800; | |
7dfde25d | 55 | |
0d863452 | 56 | # TODO: |
1c321dc6 | 57 | # - think about versioned features (use feature switch => 2) |
0d863452 RH |
58 | |
59 | =head1 NAME | |
60 | ||
e1b711da | 61 | feature - Perl pragma to enable new features |
0d863452 RH |
62 | |
63 | =head1 SYNOPSIS | |
64 | ||
47e9d84a | 65 | use feature qw(say switch); |
0d863452 | 66 | given ($foo) { |
0b25e784 DG |
67 | when (1) { say "\$foo == 1" } |
68 | when ([2,3]) { say "\$foo == 2 || \$foo == 3" } | |
69 | when (/^a[bc]d$/) { say "\$foo eq 'abd' || \$foo eq 'acd'" } | |
70 | when ($_ > 100) { say "\$foo > 100" } | |
71 | default { say "None of the above" } | |
0d863452 RH |
72 | } |
73 | ||
ec488c7f RGS |
74 | use feature ':5.10'; # loads all features available in perl 5.10 |
75 | ||
0b25e784 DG |
76 | use v5.10; # implicitly loads :5.10 feature bundle |
77 | ||
0d863452 RH |
78 | =head1 DESCRIPTION |
79 | ||
80 | It is usually impossible to add new syntax to Perl without breaking | |
b22bbcf0 | 81 | some existing programs. This pragma provides a way to minimize that |
1863b879 RGS |
82 | risk. New syntactic constructs, or new semantic meanings to older |
83 | constructs, can be enabled by C<use feature 'foo'>, and will be parsed | |
b22bbcf0 | 84 | only when the appropriate feature pragma is in scope. (Nevertheless, the |
4a904372 FC |
85 | C<CORE::> prefix provides access to all Perl keywords, regardless of this |
86 | pragma.) | |
0d863452 | 87 | |
9eb27be9 RGS |
88 | =head2 Lexical effect |
89 | ||
90 | Like other pragmas (C<use strict>, for example), features have a lexical | |
301381dc | 91 | effect. C<use feature qw(foo)> will only make the feature "foo" available |
9eb27be9 RGS |
92 | from that point to the end of the enclosing block. |
93 | ||
94 | { | |
95 | use feature 'say'; | |
96 | say "say is available here"; | |
97 | } | |
98 | print "But not here.\n"; | |
99 | ||
5e36ed56 RGS |
100 | =head2 C<no feature> |
101 | ||
b22bbcf0 | 102 | Features can also be turned off by using C<no feature "foo">. This too |
5e36ed56 RGS |
103 | has lexical effect. |
104 | ||
105 | use feature 'say'; | |
106 | say "say is available here"; | |
107 | { | |
108 | no feature 'say'; | |
109 | print "But not here.\n"; | |
110 | } | |
111 | say "Yet it is here."; | |
112 | ||
39ec54a5 RS |
113 | C<no feature> with no features specified will reset to the default group. To |
114 | disable I<all> features (an unusual request!) use C<no feature ':all'>. | |
5e36ed56 | 115 | |
0b25e784 DG |
116 | =head1 AVAILABLE FEATURES |
117 | ||
0d863452 RH |
118 | =head2 The 'say' feature |
119 | ||
0b25e784 | 120 | C<use feature 'say'> tells the compiler to enable the Perl 6 style |
9eb27be9 | 121 | C<say> function. |
0d863452 RH |
122 | |
123 | See L<perlfunc/say> for details. | |
124 | ||
0b25e784 DG |
125 | This feature is available starting with Perl 5.10. |
126 | ||
127 | =head2 The 'state' feature | |
712d05cf RGS |
128 | |
129 | C<use feature 'state'> tells the compiler to enable C<state> | |
9eb27be9 | 130 | variables. |
712d05cf | 131 | |
e60bcc8b RGS |
132 | See L<perlsub/"Persistent Private Variables"> for details. |
133 | ||
0b25e784 DG |
134 | This feature is available starting with Perl 5.10. |
135 | ||
47e9d84a EB |
136 | =head2 The 'switch' feature |
137 | ||
7caca87c DB |
138 | B<WARNING>: Because the L<smartmatch operator|perlop/"Smartmatch Operator"> is |
139 | experimental, Perl will warn when you use this feature, unless you have | |
140 | explicitly disabled the warning: | |
141 | ||
142 | no warnings "experimental::smartmatch"; | |
143 | ||
47e9d84a EB |
144 | C<use feature 'switch'> tells the compiler to enable the Perl 6 |
145 | given/when construct. | |
146 | ||
48238296 | 147 | See L<perlsyn/"Switch Statements"> for details. |
47e9d84a | 148 | |
0b25e784 DG |
149 | This feature is available starting with Perl 5.10. |
150 | ||
151 | =head2 The 'unicode_strings' feature | |
1863b879 | 152 | |
850b7ec9 | 153 | C<use feature 'unicode_strings'> tells the compiler to use Unicode rules |
20db7501 KW |
154 | in all string operations executed within its scope (unless they are also |
155 | within the scope of either C<use locale> or C<use bytes>). The same applies | |
156 | to all regular expressions compiled within the scope, even if executed outside | |
2269d15c KW |
157 | it. It does not change the internal representation of strings, but only how |
158 | they are interpreted. | |
20db7501 KW |
159 | |
160 | C<no feature 'unicode_strings'> tells the compiler to use the traditional | |
850b7ec9 | 161 | Perl rules wherein the native character set rules is used unless it is |
20db7501 KW |
162 | clear to Perl that Unicode is desired. This can lead to some surprises |
163 | when the behavior suddenly changes. (See | |
164 | L<perlunicode/The "Unicode Bug"> for details.) For this reason, if you are | |
165 | potentially using Unicode in your program, the | |
166 | C<use feature 'unicode_strings'> subpragma is B<strongly> recommended. | |
167 | ||
2e2b2571 KW |
168 | This feature is available starting with Perl 5.12; was almost fully |
169 | implemented in Perl 5.14; and extended in Perl 5.16 to cover C<quotemeta>. | |
1863b879 | 170 | |
0b25e784 | 171 | =head2 The 'unicode_eval' and 'evalbytes' features |
7289c5e6 FC |
172 | |
173 | Under the C<unicode_eval> feature, Perl's C<eval> function, when passed a | |
174 | string, will evaluate it as a string of characters, ignoring any | |
175 | C<use utf8> declarations. C<use utf8> exists to declare the encoding of | |
176 | the script, which only makes sense for a stream of bytes, not a string of | |
177 | characters. Source filters are forbidden, as they also really only make | |
178 | sense on strings of bytes. Any attempt to activate a source filter will | |
179 | result in an error. | |
180 | ||
181 | The C<evalbytes> feature enables the C<evalbytes> keyword, which evaluates | |
182 | the argument passed to it as a string of bytes. It dies if the string | |
183 | contains any characters outside the 8-bit range. Source filters work | |
184 | within C<evalbytes>: they apply to the contents of the string being | |
185 | evaluated. | |
186 | ||
187 | Together, these two features are intended to replace the historical C<eval> | |
188 | function, which has (at least) two bugs in it, that cannot easily be fixed | |
189 | without breaking existing programs: | |
190 | ||
191 | =over | |
192 | ||
193 | =item * | |
194 | ||
195 | C<eval> behaves differently depending on the internal encoding of the | |
196 | string, sometimes treating its argument as a string of bytes, and sometimes | |
197 | as a string of characters. | |
198 | ||
199 | =item * | |
200 | ||
201 | Source filters activated within C<eval> leak out into whichever I<file> | |
202 | scope is currently being compiled. To give an example with the CPAN module | |
203 | L<Semi::Semicolons>: | |
204 | ||
205 | BEGIN { eval "use Semi::Semicolons; # not filtered here " } | |
206 | # filtered here! | |
207 | ||
208 | C<evalbytes> fixes that to work the way one would expect: | |
209 | ||
210 | use feature "evalbytes"; | |
211 | BEGIN { evalbytes "use Semi::Semicolons; # filtered " } | |
212 | # not filtered | |
213 | ||
214 | =back | |
215 | ||
216 | These two features are available starting with Perl 5.16. | |
217 | ||
84ed0108 FC |
218 | =head2 The 'current_sub' feature |
219 | ||
220 | This provides the C<__SUB__> token that returns a reference to the current | |
221 | subroutine or C<undef> outside of a subroutine. | |
222 | ||
223 | This feature is available starting with Perl 5.16. | |
224 | ||
01868d00 FC |
225 | =head2 The 'array_base' feature |
226 | ||
227 | This feature supports the legacy C<$[> variable. See L<perlvar/$[> and | |
228 | L<arybase>. It is on by default but disabled under C<use v5.16> (see | |
229 | L</IMPLICIT LOADING>, below). | |
230 | ||
231 | This feature is available under this name starting with Perl 5.16. In | |
232 | previous versions, it was simply on all the time, and this pragma knew | |
233 | nothing about it. | |
234 | ||
2a4315f8 BF |
235 | =head2 The 'fc' feature |
236 | ||
237 | C<use feature 'fc'> tells the compiler to enable the C<fc> function, | |
238 | which implements Unicode casefolding. | |
239 | ||
240 | See L<perlfunc/fc> for details. | |
241 | ||
242 | This feature is available from Perl 5.16 onwards. | |
243 | ||
ca40957e FC |
244 | =head2 The 'lexical_subs' feature |
245 | ||
246 | B<WARNING>: This feature is still experimental and the implementation may | |
64fbf0dd FC |
247 | change in future versions of Perl. For this reason, Perl will |
248 | warn when you use the feature, unless you have explicitly disabled the | |
ca40957e FC |
249 | warning: |
250 | ||
f1d34ca8 | 251 | no warnings "experimental::lexical_subs"; |
ca40957e FC |
252 | |
253 | This enables declaration of subroutines via C<my sub foo>, C<state sub foo> | |
254 | and C<our sub foo> syntax. See L<perlsub/Lexical Subroutines> for details. | |
255 | ||
256 | This feature is available from Perl 5.18 onwards. | |
257 | ||
30d9c59b Z |
258 | =head2 The 'signatures' feature |
259 | ||
260 | B<WARNING>: This feature is still experimental and the implementation may | |
261 | change in future versions of Perl. For this reason, Perl will | |
262 | warn when you use the feature, unless you have explicitly disabled the | |
263 | warning: | |
264 | ||
265 | no warnings "experimental::signatures"; | |
266 | ||
267 | This enables unpacking of subroutine arguments into lexical variables | |
268 | by syntax such as | |
269 | ||
270 | sub foo ($left, $right) { | |
271 | return $left + $right; | |
272 | } | |
273 | ||
274 | See L<perlsub/Signatures> for details. | |
275 | ||
276 | This feature is available from Perl 5.20 onwards. | |
277 | ||
baabe3fb | 278 | =head2 The 'refaliasing' feature |
82848c10 FC |
279 | |
280 | B<WARNING>: This feature is still experimental and the implementation may | |
281 | change in future versions of Perl. For this reason, Perl will | |
282 | warn when you use the feature, unless you have explicitly disabled the | |
283 | warning: | |
284 | ||
baabe3fb | 285 | no warnings "experimental::refaliasing"; |
82848c10 FC |
286 | |
287 | This enables aliasing via assignment to references: | |
288 | ||
289 | \$a = \$b; # $a and $b now point to the same scalar | |
290 | \@a = \@b; # to the same array | |
291 | \%a = \%b; | |
292 | \&a = \&b; | |
293 | foreach \%hash (@array_of_hash_refs) { | |
294 | ... | |
295 | } | |
296 | ||
297 | See L<perlref/Assigning to References> for details. | |
298 | ||
299 | This feature is available from Perl 5.22 onwards. | |
300 | ||
bc9b29db RH |
301 | =head1 FEATURE BUNDLES |
302 | ||
0b25e784 | 303 | It's possible to load multiple features together, using |
b22bbcf0 | 304 | a I<feature bundle>. The name of a feature bundle is prefixed with |
0b25e784 DG |
305 | a colon, to distinguish it from an actual feature. |
306 | ||
307 | use feature ":5.10"; | |
308 | ||
309 | The following feature bundles are available: | |
310 | ||
311 | bundle features included | |
312 | --------- ----------------- | |
01868d00 | 313 | :default array_base |
0b25e784 | 314 | |
01868d00 | 315 | :5.10 say state switch array_base |
0b25e784 | 316 | |
01868d00 | 317 | :5.12 say state switch unicode_strings array_base |
0b25e784 | 318 | |
01868d00 | 319 | :5.14 say state switch unicode_strings array_base |
0b25e784 DG |
320 | |
321 | :5.16 say state switch unicode_strings | |
2a4315f8 | 322 | unicode_eval evalbytes current_sub fc |
0b25e784 | 323 | |
52fc5c56 FC |
324 | :5.18 say state switch unicode_strings |
325 | unicode_eval evalbytes current_sub fc | |
326 | ||
d09258e7 RS |
327 | :5.20 say state switch unicode_strings |
328 | unicode_eval evalbytes current_sub fc | |
329 | ||
b530a4ea RS |
330 | :5.22 say state switch unicode_strings |
331 | unicode_eval evalbytes current_sub fc | |
332 | ||
01868d00 FC |
333 | The C<:default> bundle represents the feature set that is enabled before |
334 | any C<use feature> or C<no feature> declaration. | |
a3a91442 JV |
335 | |
336 | Specifying sub-versions such as the C<0> in C<5.14.0> in feature bundles has | |
b22bbcf0 | 337 | no effect. Feature bundles are guaranteed to be the same for all sub-versions. |
bc9b29db | 338 | |
0b25e784 DG |
339 | use feature ":5.14.0"; # same as ":5.14" |
340 | use feature ":5.14.1"; # same as ":5.14" | |
a3a91442 | 341 | |
7dfde25d RGS |
342 | =head1 IMPLICIT LOADING |
343 | ||
0b25e784 DG |
344 | Instead of loading feature bundles by name, it is easier to let Perl do |
345 | implicit loading of a feature bundle for you. | |
346 | ||
347 | There are two ways to load the C<feature> pragma implicitly: | |
7dfde25d RGS |
348 | |
349 | =over 4 | |
350 | ||
351 | =item * | |
352 | ||
0b25e784 DG |
353 | By using the C<-E> switch on the Perl command-line instead of C<-e>. |
354 | That will enable the feature bundle for that version of Perl in the | |
355 | main compilation unit (that is, the one-liner that follows C<-E>). | |
7dfde25d RGS |
356 | |
357 | =item * | |
358 | ||
0b25e784 | 359 | By explicitly requiring a minimum Perl version number for your program, with |
b22bbcf0 | 360 | the C<use VERSION> construct. That is, |
7dfde25d | 361 | |
0b25e784 | 362 | use v5.10.0; |
7dfde25d RGS |
363 | |
364 | will do an implicit | |
365 | ||
39ec54a5 | 366 | no feature ':all'; |
82cfb3a2 | 367 | use feature ':5.10'; |
7dfde25d | 368 | |
b22bbcf0 FC |
369 | and so on. Note how the trailing sub-version |
370 | is automatically stripped from the | |
82cfb3a2 | 371 | version. |
7dfde25d | 372 | |
8d115822 RB |
373 | But to avoid portability warnings (see L<perlfunc/use>), you may prefer: |
374 | ||
375 | use 5.010; | |
376 | ||
377 | with the same effect. | |
378 | ||
0b25e784 | 379 | If the required version is older than Perl 5.10, the ":default" feature |
01868d00 | 380 | bundle is automatically loaded instead. |
70397346 | 381 | |
7dfde25d RGS |
382 | =back |
383 | ||
0d863452 RH |
384 | =cut |
385 | ||
386 | sub import { | |
0d863452 | 387 | my $class = shift; |
36143a0c NC |
388 | |
389 | if (!@_) { | |
0b25e784 | 390 | croak("No features specified"); |
0d863452 | 391 | } |
36143a0c | 392 | |
d3757264 | 393 | __common(1, @_); |
0d863452 RH |
394 | } |
395 | ||
396 | sub unimport { | |
397 | my $class = shift; | |
398 | ||
39ec54a5 | 399 | # A bare C<no feature> should reset to the default bundle |
bc9b29db | 400 | if (!@_) { |
39ec54a5 RS |
401 | $^H &= ~($hint_uni8bit|$hint_mask); |
402 | return; | |
bc9b29db RH |
403 | } |
404 | ||
d3757264 NC |
405 | __common(0, @_); |
406 | } | |
407 | ||
408 | ||
409 | sub __common { | |
410 | my $import = shift; | |
0c8d5017 NC |
411 | my $bundle_number = $^H & $hint_mask; |
412 | my $features = $bundle_number != $hint_mask | |
413 | && $feature_bundle{$hint_bundles[$bundle_number >> $hint_shift]}; | |
414 | if ($features) { | |
da5b5421 | 415 | # Features are enabled implicitly via bundle hints. |
d9ee6ccb NC |
416 | # Delete any keys that may be left over from last time. |
417 | delete @^H{ values(%feature) }; | |
418 | $^H |= $hint_mask; | |
419 | for (@$features) { | |
420 | $^H{$feature{$_}} = 1; | |
421 | $^H |= $hint_uni8bit if $_ eq 'unicode_strings'; | |
422 | } | |
da5b5421 | 423 | } |
bc9b29db | 424 | while (@_) { |
0b25e784 DG |
425 | my $name = shift; |
426 | if (substr($name, 0, 1) eq ":") { | |
427 | my $v = substr($name, 1); | |
428 | if (!exists $feature_bundle{$v}) { | |
429 | $v =~ s/^([0-9]+)\.([0-9]+).[0-9]+$/$1.$2/; | |
430 | if (!exists $feature_bundle{$v}) { | |
431 | unknown_feature_bundle(substr($name, 1)); | |
432 | } | |
433 | } | |
434 | unshift @_, @{$feature_bundle{$v}}; | |
435 | next; | |
436 | } | |
36143a0c | 437 | if (!exists $feature{$name}) { |
0b25e784 DG |
438 | unknown_feature($name); |
439 | } | |
d3757264 NC |
440 | if ($import) { |
441 | $^H{$feature{$name}} = 1; | |
442 | $^H |= $hint_uni8bit if $name eq 'unicode_strings'; | |
443 | } else { | |
0b25e784 | 444 | delete $^H{$feature{$name}}; |
1863b879 | 445 | $^H &= ~ $hint_uni8bit if $name eq 'unicode_strings'; |
0b25e784 | 446 | } |
0d863452 | 447 | } |
0d863452 RH |
448 | } |
449 | ||
b42943c4 RGS |
450 | sub unknown_feature { |
451 | my $feature = shift; | |
452 | croak(sprintf('Feature "%s" is not supported by Perl %vd', | |
0b25e784 | 453 | $feature, $^V)); |
b42943c4 RGS |
454 | } |
455 | ||
456 | sub unknown_feature_bundle { | |
457 | my $feature = shift; | |
458 | croak(sprintf('Feature bundle "%s" is not supported by Perl %vd', | |
0b25e784 | 459 | $feature, $^V)); |
b42943c4 RGS |
460 | } |
461 | ||
462 | sub croak { | |
463 | require Carp; | |
464 | Carp::croak(@_); | |
465 | } | |
466 | ||
0d863452 | 467 | 1; |
69bcf1d3 FC |
468 | |
469 | # ex: set ro: |