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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 | ||
b530a4ea | 8 | our $VERSION = '1.37'; |
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__', |
ebd25686 | 20 | lexical_subs => 'feature_lexsubs', |
158becca | 21 | postderef_qq => 'feature_postderef_qq', |
cda6b701 | 22 | unicode_eval => 'feature_unieval', |
47e9d84a | 23 | unicode_strings => 'feature_unicode', |
bc9b29db RH |
24 | ); |
25 | ||
0d2bd2aa | 26 | our %feature_bundle = ( |
69bcf1d3 FC |
27 | "5.10" => [qw(array_base say state switch)], |
28 | "5.11" => [qw(array_base say state switch unicode_strings)], | |
2a4315f8 | 29 | "5.15" => [qw(current_sub evalbytes fc say state switch unicode_eval unicode_strings)], |
30d9c59b | 30 | "all" => [qw(array_base current_sub evalbytes fc lexical_subs postderef postderef_qq say signatures state switch unicode_eval unicode_strings)], |
69bcf1d3 | 31 | "default" => [qw(array_base)], |
0d863452 | 32 | ); |
d052521a | 33 | |
88da30d7 FC |
34 | $feature_bundle{"5.12"} = $feature_bundle{"5.11"}; |
35 | $feature_bundle{"5.13"} = $feature_bundle{"5.11"}; | |
36 | $feature_bundle{"5.14"} = $feature_bundle{"5.11"}; | |
37 | $feature_bundle{"5.16"} = $feature_bundle{"5.15"}; | |
d6402ebe | 38 | $feature_bundle{"5.17"} = $feature_bundle{"5.15"}; |
52fc5c56 | 39 | $feature_bundle{"5.18"} = $feature_bundle{"5.15"}; |
d09258e7 RS |
40 | $feature_bundle{"5.19"} = $feature_bundle{"5.15"}; |
41 | $feature_bundle{"5.20"} = $feature_bundle{"5.15"}; | |
b530a4ea RS |
42 | $feature_bundle{"5.21"} = $feature_bundle{"5.15"}; |
43 | $feature_bundle{"5.22"} = $feature_bundle{"5.15"}; | |
88da30d7 | 44 | $feature_bundle{"5.9.5"} = $feature_bundle{"5.10"}; |
69bcf1d3 | 45 | |
0bb01b05 FC |
46 | our $hint_shift = 26; |
47 | our $hint_mask = 0x1c000000; | |
48 | our @hint_bundles = qw( default 5.10 5.11 5.15 ); | |
ada44f8c | 49 | |
69bcf1d3 FC |
50 | # This gets set (for now) in $^H as well as in %^H, |
51 | # for runtime speed of the uc/lc/ucfirst/lcfirst functions. | |
52 | # See HINT_UNI_8_BIT in perl.h. | |
53 | our $hint_uni8bit = 0x00000800; | |
7dfde25d | 54 | |
0d863452 | 55 | # TODO: |
1c321dc6 | 56 | # - think about versioned features (use feature switch => 2) |
0d863452 RH |
57 | |
58 | =head1 NAME | |
59 | ||
e1b711da | 60 | feature - Perl pragma to enable new features |
0d863452 RH |
61 | |
62 | =head1 SYNOPSIS | |
63 | ||
47e9d84a | 64 | use feature qw(say switch); |
0d863452 | 65 | given ($foo) { |
0b25e784 DG |
66 | when (1) { say "\$foo == 1" } |
67 | when ([2,3]) { say "\$foo == 2 || \$foo == 3" } | |
68 | when (/^a[bc]d$/) { say "\$foo eq 'abd' || \$foo eq 'acd'" } | |
69 | when ($_ > 100) { say "\$foo > 100" } | |
70 | default { say "None of the above" } | |
0d863452 RH |
71 | } |
72 | ||
ec488c7f RGS |
73 | use feature ':5.10'; # loads all features available in perl 5.10 |
74 | ||
0b25e784 DG |
75 | use v5.10; # implicitly loads :5.10 feature bundle |
76 | ||
0d863452 RH |
77 | =head1 DESCRIPTION |
78 | ||
79 | It is usually impossible to add new syntax to Perl without breaking | |
b22bbcf0 | 80 | some existing programs. This pragma provides a way to minimize that |
1863b879 RGS |
81 | risk. New syntactic constructs, or new semantic meanings to older |
82 | constructs, can be enabled by C<use feature 'foo'>, and will be parsed | |
b22bbcf0 | 83 | only when the appropriate feature pragma is in scope. (Nevertheless, the |
4a904372 FC |
84 | C<CORE::> prefix provides access to all Perl keywords, regardless of this |
85 | pragma.) | |
0d863452 | 86 | |
9eb27be9 RGS |
87 | =head2 Lexical effect |
88 | ||
89 | Like other pragmas (C<use strict>, for example), features have a lexical | |
301381dc | 90 | effect. C<use feature qw(foo)> will only make the feature "foo" available |
9eb27be9 RGS |
91 | from that point to the end of the enclosing block. |
92 | ||
93 | { | |
94 | use feature 'say'; | |
95 | say "say is available here"; | |
96 | } | |
97 | print "But not here.\n"; | |
98 | ||
5e36ed56 RGS |
99 | =head2 C<no feature> |
100 | ||
b22bbcf0 | 101 | Features can also be turned off by using C<no feature "foo">. This too |
5e36ed56 RGS |
102 | has lexical effect. |
103 | ||
104 | use feature 'say'; | |
105 | say "say is available here"; | |
106 | { | |
107 | no feature 'say'; | |
108 | print "But not here.\n"; | |
109 | } | |
110 | say "Yet it is here."; | |
111 | ||
39ec54a5 RS |
112 | C<no feature> with no features specified will reset to the default group. To |
113 | disable I<all> features (an unusual request!) use C<no feature ':all'>. | |
5e36ed56 | 114 | |
0b25e784 DG |
115 | =head1 AVAILABLE FEATURES |
116 | ||
0d863452 RH |
117 | =head2 The 'say' feature |
118 | ||
0b25e784 | 119 | C<use feature 'say'> tells the compiler to enable the Perl 6 style |
9eb27be9 | 120 | C<say> function. |
0d863452 RH |
121 | |
122 | See L<perlfunc/say> for details. | |
123 | ||
0b25e784 DG |
124 | This feature is available starting with Perl 5.10. |
125 | ||
126 | =head2 The 'state' feature | |
712d05cf RGS |
127 | |
128 | C<use feature 'state'> tells the compiler to enable C<state> | |
9eb27be9 | 129 | variables. |
712d05cf | 130 | |
e60bcc8b RGS |
131 | See L<perlsub/"Persistent Private Variables"> for details. |
132 | ||
0b25e784 DG |
133 | This feature is available starting with Perl 5.10. |
134 | ||
47e9d84a EB |
135 | =head2 The 'switch' feature |
136 | ||
137 | C<use feature 'switch'> tells the compiler to enable the Perl 6 | |
138 | given/when construct. | |
139 | ||
48238296 | 140 | See L<perlsyn/"Switch Statements"> for details. |
47e9d84a | 141 | |
0b25e784 DG |
142 | This feature is available starting with Perl 5.10. |
143 | ||
144 | =head2 The 'unicode_strings' feature | |
1863b879 | 145 | |
850b7ec9 | 146 | C<use feature 'unicode_strings'> tells the compiler to use Unicode rules |
20db7501 KW |
147 | in all string operations executed within its scope (unless they are also |
148 | within the scope of either C<use locale> or C<use bytes>). The same applies | |
149 | to all regular expressions compiled within the scope, even if executed outside | |
2269d15c KW |
150 | it. It does not change the internal representation of strings, but only how |
151 | they are interpreted. | |
20db7501 KW |
152 | |
153 | C<no feature 'unicode_strings'> tells the compiler to use the traditional | |
850b7ec9 | 154 | Perl rules wherein the native character set rules is used unless it is |
20db7501 KW |
155 | clear to Perl that Unicode is desired. This can lead to some surprises |
156 | when the behavior suddenly changes. (See | |
157 | L<perlunicode/The "Unicode Bug"> for details.) For this reason, if you are | |
158 | potentially using Unicode in your program, the | |
159 | C<use feature 'unicode_strings'> subpragma is B<strongly> recommended. | |
160 | ||
2e2b2571 KW |
161 | This feature is available starting with Perl 5.12; was almost fully |
162 | implemented in Perl 5.14; and extended in Perl 5.16 to cover C<quotemeta>. | |
1863b879 | 163 | |
0b25e784 | 164 | =head2 The 'unicode_eval' and 'evalbytes' features |
7289c5e6 FC |
165 | |
166 | Under the C<unicode_eval> feature, Perl's C<eval> function, when passed a | |
167 | string, will evaluate it as a string of characters, ignoring any | |
168 | C<use utf8> declarations. C<use utf8> exists to declare the encoding of | |
169 | the script, which only makes sense for a stream of bytes, not a string of | |
170 | characters. Source filters are forbidden, as they also really only make | |
171 | sense on strings of bytes. Any attempt to activate a source filter will | |
172 | result in an error. | |
173 | ||
174 | The C<evalbytes> feature enables the C<evalbytes> keyword, which evaluates | |
175 | the argument passed to it as a string of bytes. It dies if the string | |
176 | contains any characters outside the 8-bit range. Source filters work | |
177 | within C<evalbytes>: they apply to the contents of the string being | |
178 | evaluated. | |
179 | ||
180 | Together, these two features are intended to replace the historical C<eval> | |
181 | function, which has (at least) two bugs in it, that cannot easily be fixed | |
182 | without breaking existing programs: | |
183 | ||
184 | =over | |
185 | ||
186 | =item * | |
187 | ||
188 | C<eval> behaves differently depending on the internal encoding of the | |
189 | string, sometimes treating its argument as a string of bytes, and sometimes | |
190 | as a string of characters. | |
191 | ||
192 | =item * | |
193 | ||
194 | Source filters activated within C<eval> leak out into whichever I<file> | |
195 | scope is currently being compiled. To give an example with the CPAN module | |
196 | L<Semi::Semicolons>: | |
197 | ||
198 | BEGIN { eval "use Semi::Semicolons; # not filtered here " } | |
199 | # filtered here! | |
200 | ||
201 | C<evalbytes> fixes that to work the way one would expect: | |
202 | ||
203 | use feature "evalbytes"; | |
204 | BEGIN { evalbytes "use Semi::Semicolons; # filtered " } | |
205 | # not filtered | |
206 | ||
207 | =back | |
208 | ||
209 | These two features are available starting with Perl 5.16. | |
210 | ||
84ed0108 FC |
211 | =head2 The 'current_sub' feature |
212 | ||
213 | This provides the C<__SUB__> token that returns a reference to the current | |
214 | subroutine or C<undef> outside of a subroutine. | |
215 | ||
216 | This feature is available starting with Perl 5.16. | |
217 | ||
01868d00 FC |
218 | =head2 The 'array_base' feature |
219 | ||
220 | This feature supports the legacy C<$[> variable. See L<perlvar/$[> and | |
221 | L<arybase>. It is on by default but disabled under C<use v5.16> (see | |
222 | L</IMPLICIT LOADING>, below). | |
223 | ||
224 | This feature is available under this name starting with Perl 5.16. In | |
225 | previous versions, it was simply on all the time, and this pragma knew | |
226 | nothing about it. | |
227 | ||
2a4315f8 BF |
228 | =head2 The 'fc' feature |
229 | ||
230 | C<use feature 'fc'> tells the compiler to enable the C<fc> function, | |
231 | which implements Unicode casefolding. | |
232 | ||
233 | See L<perlfunc/fc> for details. | |
234 | ||
235 | This feature is available from Perl 5.16 onwards. | |
236 | ||
ca40957e FC |
237 | =head2 The 'lexical_subs' feature |
238 | ||
239 | B<WARNING>: This feature is still experimental and the implementation may | |
64fbf0dd FC |
240 | change in future versions of Perl. For this reason, Perl will |
241 | warn when you use the feature, unless you have explicitly disabled the | |
ca40957e FC |
242 | warning: |
243 | ||
f1d34ca8 | 244 | no warnings "experimental::lexical_subs"; |
ca40957e FC |
245 | |
246 | This enables declaration of subroutines via C<my sub foo>, C<state sub foo> | |
247 | and C<our sub foo> syntax. See L<perlsub/Lexical Subroutines> for details. | |
248 | ||
249 | This feature is available from Perl 5.18 onwards. | |
250 | ||
30d9c59b Z |
251 | =head2 The 'signatures' feature |
252 | ||
253 | B<WARNING>: This feature is still experimental and the implementation may | |
254 | change in future versions of Perl. For this reason, Perl will | |
255 | warn when you use the feature, unless you have explicitly disabled the | |
256 | warning: | |
257 | ||
258 | no warnings "experimental::signatures"; | |
259 | ||
260 | This enables unpacking of subroutine arguments into lexical variables | |
261 | by syntax such as | |
262 | ||
263 | sub foo ($left, $right) { | |
264 | return $left + $right; | |
265 | } | |
266 | ||
267 | See L<perlsub/Signatures> for details. | |
268 | ||
269 | This feature is available from Perl 5.20 onwards. | |
270 | ||
bc9b29db RH |
271 | =head1 FEATURE BUNDLES |
272 | ||
0b25e784 | 273 | It's possible to load multiple features together, using |
b22bbcf0 | 274 | a I<feature bundle>. The name of a feature bundle is prefixed with |
0b25e784 DG |
275 | a colon, to distinguish it from an actual feature. |
276 | ||
277 | use feature ":5.10"; | |
278 | ||
279 | The following feature bundles are available: | |
280 | ||
281 | bundle features included | |
282 | --------- ----------------- | |
01868d00 | 283 | :default array_base |
0b25e784 | 284 | |
01868d00 | 285 | :5.10 say state switch array_base |
0b25e784 | 286 | |
01868d00 | 287 | :5.12 say state switch unicode_strings array_base |
0b25e784 | 288 | |
01868d00 | 289 | :5.14 say state switch unicode_strings array_base |
0b25e784 DG |
290 | |
291 | :5.16 say state switch unicode_strings | |
2a4315f8 | 292 | unicode_eval evalbytes current_sub fc |
0b25e784 | 293 | |
52fc5c56 FC |
294 | :5.18 say state switch unicode_strings |
295 | unicode_eval evalbytes current_sub fc | |
296 | ||
d09258e7 RS |
297 | :5.20 say state switch unicode_strings |
298 | unicode_eval evalbytes current_sub fc | |
299 | ||
b530a4ea RS |
300 | :5.22 say state switch unicode_strings |
301 | unicode_eval evalbytes current_sub fc | |
302 | ||
01868d00 FC |
303 | The C<:default> bundle represents the feature set that is enabled before |
304 | any C<use feature> or C<no feature> declaration. | |
a3a91442 JV |
305 | |
306 | Specifying sub-versions such as the C<0> in C<5.14.0> in feature bundles has | |
b22bbcf0 | 307 | no effect. Feature bundles are guaranteed to be the same for all sub-versions. |
bc9b29db | 308 | |
0b25e784 DG |
309 | use feature ":5.14.0"; # same as ":5.14" |
310 | use feature ":5.14.1"; # same as ":5.14" | |
a3a91442 | 311 | |
7dfde25d RGS |
312 | =head1 IMPLICIT LOADING |
313 | ||
0b25e784 DG |
314 | Instead of loading feature bundles by name, it is easier to let Perl do |
315 | implicit loading of a feature bundle for you. | |
316 | ||
317 | There are two ways to load the C<feature> pragma implicitly: | |
7dfde25d RGS |
318 | |
319 | =over 4 | |
320 | ||
321 | =item * | |
322 | ||
0b25e784 DG |
323 | By using the C<-E> switch on the Perl command-line instead of C<-e>. |
324 | That will enable the feature bundle for that version of Perl in the | |
325 | main compilation unit (that is, the one-liner that follows C<-E>). | |
7dfde25d RGS |
326 | |
327 | =item * | |
328 | ||
0b25e784 | 329 | By explicitly requiring a minimum Perl version number for your program, with |
b22bbcf0 | 330 | the C<use VERSION> construct. That is, |
7dfde25d | 331 | |
0b25e784 | 332 | use v5.10.0; |
7dfde25d RGS |
333 | |
334 | will do an implicit | |
335 | ||
39ec54a5 | 336 | no feature ':all'; |
82cfb3a2 | 337 | use feature ':5.10'; |
7dfde25d | 338 | |
b22bbcf0 FC |
339 | and so on. Note how the trailing sub-version |
340 | is automatically stripped from the | |
82cfb3a2 | 341 | version. |
7dfde25d | 342 | |
8d115822 RB |
343 | But to avoid portability warnings (see L<perlfunc/use>), you may prefer: |
344 | ||
345 | use 5.010; | |
346 | ||
347 | with the same effect. | |
348 | ||
0b25e784 | 349 | If the required version is older than Perl 5.10, the ":default" feature |
01868d00 | 350 | bundle is automatically loaded instead. |
70397346 | 351 | |
7dfde25d RGS |
352 | =back |
353 | ||
0d863452 RH |
354 | =cut |
355 | ||
356 | sub import { | |
0d863452 | 357 | my $class = shift; |
36143a0c NC |
358 | |
359 | if (!@_) { | |
0b25e784 | 360 | croak("No features specified"); |
0d863452 | 361 | } |
36143a0c | 362 | |
d3757264 | 363 | __common(1, @_); |
0d863452 RH |
364 | } |
365 | ||
366 | sub unimport { | |
367 | my $class = shift; | |
368 | ||
39ec54a5 | 369 | # A bare C<no feature> should reset to the default bundle |
bc9b29db | 370 | if (!@_) { |
39ec54a5 RS |
371 | $^H &= ~($hint_uni8bit|$hint_mask); |
372 | return; | |
bc9b29db RH |
373 | } |
374 | ||
d3757264 NC |
375 | __common(0, @_); |
376 | } | |
377 | ||
378 | ||
379 | sub __common { | |
380 | my $import = shift; | |
0c8d5017 NC |
381 | my $bundle_number = $^H & $hint_mask; |
382 | my $features = $bundle_number != $hint_mask | |
383 | && $feature_bundle{$hint_bundles[$bundle_number >> $hint_shift]}; | |
384 | if ($features) { | |
da5b5421 | 385 | # Features are enabled implicitly via bundle hints. |
d9ee6ccb NC |
386 | # Delete any keys that may be left over from last time. |
387 | delete @^H{ values(%feature) }; | |
388 | $^H |= $hint_mask; | |
389 | for (@$features) { | |
390 | $^H{$feature{$_}} = 1; | |
391 | $^H |= $hint_uni8bit if $_ eq 'unicode_strings'; | |
392 | } | |
da5b5421 | 393 | } |
bc9b29db | 394 | while (@_) { |
0b25e784 DG |
395 | my $name = shift; |
396 | if (substr($name, 0, 1) eq ":") { | |
397 | my $v = substr($name, 1); | |
398 | if (!exists $feature_bundle{$v}) { | |
399 | $v =~ s/^([0-9]+)\.([0-9]+).[0-9]+$/$1.$2/; | |
400 | if (!exists $feature_bundle{$v}) { | |
401 | unknown_feature_bundle(substr($name, 1)); | |
402 | } | |
403 | } | |
404 | unshift @_, @{$feature_bundle{$v}}; | |
405 | next; | |
406 | } | |
36143a0c | 407 | if (!exists $feature{$name}) { |
0b25e784 DG |
408 | unknown_feature($name); |
409 | } | |
d3757264 NC |
410 | if ($import) { |
411 | $^H{$feature{$name}} = 1; | |
412 | $^H |= $hint_uni8bit if $name eq 'unicode_strings'; | |
413 | } else { | |
0b25e784 | 414 | delete $^H{$feature{$name}}; |
1863b879 | 415 | $^H &= ~ $hint_uni8bit if $name eq 'unicode_strings'; |
0b25e784 | 416 | } |
0d863452 | 417 | } |
0d863452 RH |
418 | } |
419 | ||
b42943c4 RGS |
420 | sub unknown_feature { |
421 | my $feature = shift; | |
422 | croak(sprintf('Feature "%s" is not supported by Perl %vd', | |
0b25e784 | 423 | $feature, $^V)); |
b42943c4 RGS |
424 | } |
425 | ||
426 | sub unknown_feature_bundle { | |
427 | my $feature = shift; | |
428 | croak(sprintf('Feature bundle "%s" is not supported by Perl %vd', | |
0b25e784 | 429 | $feature, $^V)); |
b42943c4 RGS |
430 | } |
431 | ||
432 | sub croak { | |
433 | require Carp; | |
434 | Carp::croak(@_); | |
435 | } | |
436 | ||
0d863452 | 437 | 1; |
69bcf1d3 FC |
438 | |
439 | # ex: set ro: |