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1 | <?xml version="1.0" encoding="utf-8"?> |
2 | <!-- | |
3 | Copyright 2012 Eric Niebler | |
4 | ||
5 | Distributed under the Boost | |
6 | Software License, Version 1.0. (See accompanying | |
7 | file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt) | |
8 | --> | |
9 | <header name="boost/proto/transform/env.hpp"> | |
10 | <namespace name="boost"> | |
11 | <namespace name="proto"> | |
12 | ||
13 | <struct name="key_not_found"> | |
14 | <purpose> | |
15 | The type of objects returned when a key-based lookup fails in a | |
16 | transform environment. | |
17 | </purpose> | |
18 | </struct> | |
19 | ||
20 | <!-- empty_env --> | |
21 | <struct name="empty_env"> | |
22 | <purpose> | |
23 | The type of an object that represents a transform environment | |
24 | with no key/value pairs in it. | |
25 | </purpose> | |
26 | ||
27 | <method-group name="public member functions"> | |
28 | <method name="operator[]" cv="const"> | |
29 | <type><classname>proto::key_not_found</classname></type> | |
30 | <parameter name=""> | |
31 | <paramtype><replaceable>unspecified</replaceable></paramtype> | |
32 | </parameter> | |
33 | <description> | |
34 | <para>The type of the argument to this function has a | |
35 | user-defined implicit conversion from any type.</para> | |
36 | </description> | |
37 | </method> | |
38 | </method-group> | |
39 | </struct> | |
40 | ||
41 | <!-- env --> | |
42 | <struct name="env"> | |
43 | <template> | |
44 | <template-type-parameter name="Key"/> | |
45 | <template-type-parameter name="Value"/> | |
46 | <template-type-parameter name="Env"> | |
47 | <default><classname>proto::empty_env</classname></default> | |
48 | </template-type-parameter> | |
49 | </template> | |
50 | ||
51 | <constructor specifiers="explicit"> | |
52 | <parameter name="value"> | |
53 | <paramtype>Value const &</paramtype> | |
54 | <description> | |
55 | <para> | |
56 | The value to be associated with the <code>Key</code>. | |
57 | </para> | |
58 | </description> | |
59 | </parameter> | |
60 | <parameter name="other"> | |
61 | <paramtype>Env const &</paramtype> | |
62 | <default>Env()</default> | |
63 | <description> | |
64 | <para> | |
65 | Another key/value store. | |
66 | </para> | |
67 | </description> | |
68 | </parameter> | |
69 | </constructor> | |
70 | ||
71 | <method-group name="public member functions"> | |
72 | <method name="operator[]" cv="const"> | |
73 | <type><replaceable>see-below</replaceable></type> | |
74 | <parameter name=""> | |
75 | <paramtype><replaceable>see-below</replaceable></paramtype> | |
76 | </parameter> | |
77 | <description> | |
78 | <para> | |
79 | If called with an object that is implicitly convertible to type <code>Key</code>, | |
80 | this function returns the <code>Value</code> passed to the constructor. Otherwise, it returns | |
81 | the result of calling <code>operator[]</code> on the <code>Env</code> passed to | |
82 | the constructor. | |
83 | </para> | |
84 | </description> | |
85 | </method> | |
86 | </method-group> | |
87 | </struct> | |
88 | ||
89 | <!-- is_env --> | |
90 | <struct name="is_env"> | |
91 | <template> | |
92 | <template-type-parameter name="T"/> | |
93 | </template> | |
94 | <inherit><type>mpl::bool_<<replaceable>true-or-false</replaceable>></type></inherit> | |
95 | <purpose> | |
96 | <para>A Boolean metafuntion for determining whether or not a type is a Proto | |
97 | transform environment.</para> | |
98 | </purpose> | |
99 | <description> | |
100 | <para><code>is_env<T></code> inherits from <code>mpl::true_</code> under the following | |
101 | conditions: | |
102 | <itemizedlist> | |
103 | <listitem>If <code>T</code> is <classname>proto::empty_env</classname>.</listitem> | |
104 | <listitem>If <code>T</code> is a specialization of <classname>proto::env<></classname>.</listitem> | |
105 | <listitem>If <code>T</code> is derived from any of the above.</listitem> | |
106 | <listitem>If <code>T</code> is a cv-qualified variant of any of the above.</listitem> | |
107 | <listitem>If <code>T</code> is a reference to any of the above.</listitem> | |
108 | </itemizedlist> | |
109 | </para> | |
110 | <para>Otherwise, <code>is_env<T></code> inherits from <code>mpl::false_</code>. | |
111 | </para> | |
112 | </description> | |
113 | </struct> | |
114 | ||
115 | <struct name="data_type"> | |
116 | <purpose> | |
117 | The type of <code><globalname>proto::data</globalname></code>, a key for use when creating | |
118 | a transform environment that associates a piece of data with this type. | |
119 | </purpose> | |
120 | <description> | |
121 | <para> | |
122 | The <code>proto::data_type</code> type, along with the <code><globalname>proto::data</globalname></code> | |
123 | global, are declared using the <code><macroname>BOOST_PROTO_DEFINE_ENV_VAR</macroname>()</code> macro. | |
124 | </para> | |
125 | </description> | |
126 | <method-group name="public member functions"> | |
127 | <overloaded-method name="operator="> | |
128 | <signature cv="const"> | |
129 | <template> | |
130 | <template-type-parameter name="Value"/> | |
131 | </template> | |
132 | <type><classname>env</classname><data_type, <replaceable>see-below</replaceable>></type> | |
133 | <parameter name="value"> | |
134 | <paramtype>Value &</paramtype> | |
135 | </parameter> | |
136 | </signature> | |
137 | <signature cv="const"> | |
138 | <template> | |
139 | <template-type-parameter name="Value"/> | |
140 | </template> | |
141 | <type><classname>env</classname><data_type, <replaceable>see-below</replaceable>></type> | |
142 | <parameter name="value"> | |
143 | <paramtype>Value const &</paramtype> | |
144 | </parameter> | |
145 | </signature> | |
146 | <description> | |
147 | <para> | |
148 | If <code>Value</code> is a specialization <code>boost::reference_wrapper<T></code>, | |
149 | this function returns <code><classname>env</classname><data_type, T &>(value.get())</code>. | |
150 | </para> | |
151 | <para> | |
152 | Else, if the type <code>Value</code> is non-copyable (i.e., a function, an array, abstract, or an ostream), | |
153 | this function returns <code><classname>env</classname><data_type, Value <replaceable>cv</replaceable> &>(value)</code>, | |
154 | where <code><replaceable>cv</replaceable></code> is <code>const</code> for the second overload, and empty | |
155 | for the first. | |
156 | </para> | |
157 | <para> | |
158 | Otherwise, this function returns <code><classname>env</classname><data_type, Value>(value)</code>. | |
159 | </para> | |
160 | </description> | |
161 | </overloaded-method> | |
162 | </method-group> | |
163 | </struct> | |
164 | ||
165 | <data-member name="data"> | |
166 | <description> | |
167 | <para>A key used for creating a transform environment.</para> | |
168 | </description> | |
169 | <type><classname>proto::data_type</classname> const</type> | |
170 | </data-member> | |
171 | ||
172 | <namespace name="functional"> | |
173 | ||
174 | <!-- functional::as_env --> | |
175 | <struct name="as_env"> | |
176 | <inherit><classname>proto::callable</classname></inherit> | |
177 | <purpose> | |
178 | A unary <conceptname>PolymorphicFunctionObject</conceptname> for ensuring that an object | |
179 | is a transform environment. If it isn't already, it is turned into one such that the | |
180 | object is associated with the <classname>proto::data_type</classname> key. | |
181 | </purpose> | |
182 | <struct name="result"> | |
183 | <template> | |
184 | <template-type-parameter name="Sig"/> | |
185 | </template> | |
186 | <typedef name="type"> | |
187 | <type><replaceable>see-below</replaceable></type> | |
188 | <description> | |
189 | <para>See <code><methodname>proto::functional::as_env::operator()</methodname></code>.</para> | |
190 | </description> | |
191 | </typedef> | |
192 | <description> | |
193 | <para> | |
194 | Encodes the return type of <code><methodname>proto::functional::as_env::operator()</methodname></code>. | |
195 | The presence of this member template makes <code><classname>proto::functional::as_env</classname></code> | |
196 | a valid TR1-style function object type usable with <code>boost::result_of<></code>. | |
197 | </para> | |
198 | </description> | |
199 | </struct> | |
200 | <method-group name="public member functions"> | |
201 | <overloaded-method name="operator()"> | |
202 | <signature cv="const"> | |
203 | <template> | |
204 | <template-type-parameter name="T"/> | |
205 | </template> | |
206 | <type><replaceable>see-below</replaceable></type> | |
207 | <parameter name="t"> | |
208 | <paramtype>T &</paramtype> | |
209 | </parameter> | |
210 | </signature> | |
211 | <signature cv="const"> | |
212 | <template> | |
213 | <template-type-parameter name="T"/> | |
214 | </template> | |
215 | <type><replaceable>see-below</replaceable></type> | |
216 | <parameter name="t"> | |
217 | <paramtype>T const &</paramtype> | |
218 | </parameter> | |
219 | </signature> | |
220 | <description> | |
221 | <para> | |
222 | If <code><classname>proto::is_env</classname><T>::value</code> is <code>false</code>, | |
223 | this function returns the result of <code>(<globalname>proto::data</globalname> = t)</code>. | |
224 | See <code><methodname>proto::data_type::operator=</methodname></code> for details. | |
225 | </para> | |
226 | <para> | |
227 | Otherwise, this function returns <code>t</code> by reference. | |
228 | </para> | |
229 | </description> | |
230 | </overloaded-method> | |
231 | </method-group> | |
232 | </struct> | |
233 | ||
234 | <!-- functional::has_env_var --> | |
235 | <struct name="has_env_var"> | |
236 | <inherit><classname>proto::callable</classname></inherit> | |
237 | <template> | |
238 | <template-type-parameter name="Key"/> | |
239 | </template> | |
240 | <purpose> | |
241 | A unary boolean <conceptname>PolymorphicFunctionObject</conceptname> used for determining whether a particular | |
242 | transform environment has a value associated with a particular key. | |
243 | </purpose> | |
244 | <struct name="result"> | |
245 | <template> | |
246 | <template-type-parameter name="Sig"/> | |
247 | </template> | |
248 | <typedef name="type"> | |
249 | <type><replaceable>see-below</replaceable></type> | |
250 | <description> | |
251 | <para>See <code><methodname>proto::functional::has_env_var::operator()</methodname></code>.</para> | |
252 | </description> | |
253 | </typedef> | |
254 | <description> | |
255 | <para> | |
256 | Encodes the return type of <code><methodname>proto::functional::has_env_var::operator()</methodname></code>. | |
257 | The presence of this member template makes <code><classname>proto::functional::has_env_var</classname></code> | |
258 | a valid TR1-style function object type usable with <code>boost::result_of<></code>. | |
259 | </para> | |
260 | </description> | |
261 | </struct> | |
262 | <method-group name="public member functions"> | |
263 | <method name="operator()" cv="const"> | |
264 | <template> | |
265 | <template-type-parameter name="Env"/> | |
266 | </template> | |
267 | <type><replaceable>see-below</replaceable></type> | |
268 | <parameter name="e"> | |
269 | <paramtype>Env const &</paramtype> | |
270 | </parameter> | |
271 | <description> | |
272 | <para> | |
273 | This function behaves as follows: | |
274 | <itemizedlist> | |
275 | <listitem> | |
276 | If <code><classname>proto::is_env</classname><Env>::value</code> is <code>true</code>: | |
277 | <itemizedlist> | |
278 | <listitem> | |
279 | If <code>e[Key()]</code> returns an instance of | |
280 | <code><classname>proto::key_not_found</classname></code>, return | |
281 | <code>mpl::false_</code>. See <code><methodname>proto::env::operator[]</methodname></code> | |
282 | for more information. | |
283 | </listitem> | |
284 | <listitem> | |
285 | Otherwise, return <code>mpl::true_</code>. | |
286 | </listitem> | |
287 | </itemizedlist> | |
288 | </listitem> | |
289 | <listitem> | |
290 | Otherwise: | |
291 | <itemizedlist> | |
292 | <listitem> | |
293 | If <code>Key</code> is <code><classname>proto::data_type</classname></code>, | |
294 | return <code>mpl::true_</code>. | |
295 | </listitem> | |
296 | <listitem> | |
297 | Otherwise, return <code>mpl::false_</code>. | |
298 | </listitem> | |
299 | </itemizedlist> | |
300 | </listitem> | |
301 | </itemizedlist> | |
302 | </para> | |
303 | </description> | |
304 | </method> | |
305 | </method-group> | |
306 | </struct> | |
307 | ||
308 | <!-- functional::env_var --> | |
309 | <struct name="env_var"> | |
310 | <inherit><classname>proto::callable</classname></inherit> | |
311 | <template> | |
312 | <template-type-parameter name="Key"/> | |
313 | </template> | |
314 | <purpose> | |
315 | A unary <conceptname>PolymorphicFunctionObject</conceptname> used for fetching the value | |
316 | associated with a particular key in a transform environment. | |
317 | </purpose> | |
318 | <struct name="result"> | |
319 | <template> | |
320 | <template-type-parameter name="Sig"/> | |
321 | </template> | |
322 | <typedef name="type"> | |
323 | <type><replaceable>see-below</replaceable></type> | |
324 | <description> | |
325 | <para>See <code><methodname>proto::functional::env_var::operator()</methodname></code>.</para> | |
326 | </description> | |
327 | </typedef> | |
328 | <description> | |
329 | <para> | |
330 | Encodes the return type of <code><methodname>proto::functional::env_var::operator()</methodname></code>. | |
331 | The presence of this member template makes <code><classname>proto::functional::env_var</classname></code> | |
332 | a valid TR1-style function object type usable with <code>boost::result_of<></code>. | |
333 | </para> | |
334 | </description> | |
335 | </struct> | |
336 | <method-group name="public member functions"> | |
337 | <method name="operator()" cv="const"> | |
338 | <template> | |
339 | <template-type-parameter name="Env"/> | |
340 | </template> | |
341 | <type><replaceable>see-below</replaceable></type> | |
342 | <parameter name="e"> | |
343 | <paramtype>Env const &</paramtype> | |
344 | </parameter> | |
345 | <description> | |
346 | <para> | |
347 | This function behaves as follows: | |
348 | <itemizedlist> | |
349 | <listitem> | |
350 | If <code>Key</code> is <code><classname>proto::data_type</classname></code>: | |
351 | <itemizedlist> | |
352 | <listitem> | |
353 | If <code><classname>proto::is_env</classname><Env>::value</code> is <code>true</code>, | |
354 | return <code>e[<globalname>proto::data</globalname>]</code>. | |
355 | </listitem> | |
356 | <listitem> | |
357 | Otherwise, return <code>e</code>. | |
358 | </listitem> | |
359 | </itemizedlist> | |
360 | </listitem> | |
361 | <listitem> | |
362 | Otherwise, return <code>e[Key()]</code>. | |
363 | </listitem> | |
364 | </itemizedlist> | |
365 | </para> | |
366 | <para> | |
367 | See <code><methodname>proto::env::operator[]</methodname></code> for additional information. | |
368 | </para> | |
369 | </description> | |
370 | </method> | |
371 | </method-group> | |
372 | </struct> | |
373 | ||
374 | </namespace> | |
375 | ||
376 | <namespace name="result_of"> | |
377 | <struct name="as_env"> | |
378 | <template> | |
379 | <template-type-parameter name="T"/> | |
380 | </template> | |
381 | <inherit><type>boost::result_of<<classname>proto::functional::as_env</classname>(T)></type></inherit> | |
382 | <purpose> | |
383 | Metafunction for computing the return type of <code><functionname>proto::as_env()</functionname></code>. | |
384 | </purpose> | |
385 | </struct> | |
386 | <struct name="has_env_var"> | |
387 | <template> | |
388 | <template-type-parameter name="Env"/> | |
389 | <template-type-parameter name="Key"/> | |
390 | </template> | |
391 | <inherit><type>boost::result_of<<classname>proto::functional::has_env_var</classname><Key>(Env)>::type</type></inherit> | |
392 | <purpose> | |
393 | Metafunction for computing the return type of <code><functionname>proto::has_env_var()</functionname></code>. | |
394 | </purpose> | |
395 | </struct> | |
396 | <struct name="env_var"> | |
397 | <template> | |
398 | <template-type-parameter name="Env"/> | |
399 | <template-type-parameter name="Key"/> | |
400 | </template> | |
401 | <inherit><type>boost::result_of<<classname>proto::functional::env_var</classname><Key>(Env)></type></inherit> | |
402 | <purpose> | |
403 | Metafunction for computing the return type of <code><functionname>proto::env_var()</functionname></code>. | |
404 | </purpose> | |
405 | </struct> | |
406 | </namespace> | |
407 | ||
408 | <!-- proto::as_env --> | |
409 | <overloaded-function name="as_env"> | |
410 | <signature> | |
411 | <template> | |
412 | <template-type-parameter name="T"/> | |
413 | </template> | |
414 | <type>typename <classname>proto::result_of::as_env</classname><T &>::type</type> | |
415 | <parameter name="t"> | |
416 | <paramtype>T &</paramtype> | |
417 | </parameter> | |
418 | </signature> | |
419 | <signature> | |
420 | <template> | |
421 | <template-type-parameter name="T"/> | |
422 | </template> | |
423 | <type>typename <classname>proto::result_of::as_env</classname><T const &>::type</type> | |
424 | <parameter name="t"> | |
425 | <paramtype>T const &</paramtype> | |
426 | </parameter> | |
427 | </signature> | |
428 | <purpose> | |
429 | For ensuring that the given argument is a transform environment. If it is not already, | |
430 | it is made one as if by <code>(<globalname>proto::data</globalname> = t)</code>. | |
431 | </purpose> | |
432 | <description> | |
433 | <para> | |
434 | See also: | |
435 | <itemizedlist> | |
436 | <listitem> | |
437 | <code><methodname>proto::data_type::operator=</methodname></code> | |
438 | </listitem> | |
439 | <listitem> | |
440 | <code><methodname>proto::functional::as_env::operator()</methodname></code> | |
441 | </listitem> | |
442 | </itemizedlist> | |
443 | </para> | |
444 | </description> | |
445 | <returns><code><classname>proto::functional::as_env</classname>()(t)</code></returns> | |
446 | </overloaded-function> | |
447 | ||
448 | <!-- proto::has_env_var --> | |
449 | <overloaded-function name="has_env_var"> | |
450 | <signature> | |
451 | <template> | |
452 | <template-type-parameter name="Key"/> | |
453 | <template-type-parameter name="Env"/> | |
454 | </template> | |
455 | <type>typename <classname>proto::result_of::has_env_var</classname><Env &, Key>::type</type> | |
456 | <parameter name="e"> | |
457 | <paramtype>Env &</paramtype> | |
458 | </parameter> | |
459 | </signature> | |
460 | <signature> | |
461 | <template> | |
462 | <template-type-parameter name="Key"/> | |
463 | <template-type-parameter name="Env"/> | |
464 | </template> | |
465 | <type>typename <classname>proto::result_of::has_env_var</classname><Env const &, Key>::type</type> | |
466 | <parameter name="e"> | |
467 | <paramtype>Env const &</paramtype> | |
468 | </parameter> | |
469 | </signature> | |
470 | <purpose> | |
471 | For testing to see whether a value exists in a transform environment corresponding to the | |
472 | specified <code>Key</code>. | |
473 | </purpose> | |
474 | <description> | |
475 | <para> | |
476 | See also: | |
477 | <itemizedlist> | |
478 | <listitem> | |
479 | <code><methodname>proto::functional::has_env_var::operator()</methodname></code> | |
480 | </listitem> | |
481 | </itemizedlist> | |
482 | </para> | |
483 | </description> | |
484 | <returns><code><classname>proto::functional::has_env_var<Key></classname>()(e)</code></returns> | |
485 | </overloaded-function> | |
486 | ||
487 | <!-- proto::env_var --> | |
488 | <overloaded-function name="env_var"> | |
489 | <signature> | |
490 | <template> | |
491 | <template-type-parameter name="Key"/> | |
492 | <template-type-parameter name="Env"/> | |
493 | </template> | |
494 | <type>typename <classname>proto::result_of::env_var</classname><Env &, Key>::type</type> | |
495 | <parameter name="e"> | |
496 | <paramtype>Env &</paramtype> | |
497 | </parameter> | |
498 | </signature> | |
499 | <signature> | |
500 | <template> | |
501 | <template-type-parameter name="Key"/> | |
502 | <template-type-parameter name="Env"/> | |
503 | </template> | |
504 | <type>typename <classname>proto::result_of::env_var</classname><Env const &, Key>::type</type> | |
505 | <parameter name="e"> | |
506 | <paramtype>Env const &</paramtype> | |
507 | </parameter> | |
508 | </signature> | |
509 | <purpose> | |
510 | For fetching the value from a transform environment corresponding to the | |
511 | specified <code>Key</code>. | |
512 | </purpose> | |
513 | <description> | |
514 | <para> | |
515 | See also: | |
516 | <itemizedlist> | |
517 | <listitem> | |
518 | <code><methodname>proto::functional::env_var::operator()</methodname></code> | |
519 | </listitem> | |
520 | </itemizedlist> | |
521 | </para> | |
522 | </description> | |
523 | <returns><code><classname>proto::functional::env_var<Key></classname>()(e)</code></returns> | |
524 | </overloaded-function> | |
525 | ||
526 | <!-- proto::operator, --> | |
527 | <overloaded-function name="operator,"> | |
528 | <signature> | |
529 | <template> | |
530 | <template-type-parameter name="Env"/> | |
531 | <template-type-parameter name="Key"/> | |
532 | <template-type-parameter name="Value"/> | |
533 | </template> | |
534 | <type><classname>proto::env</classname><Key, Value, <replaceable>UNCVREF</replaceable>(typename <classname>proto::result_of::as_env</classname><Env &>::type)></type> | |
535 | <parameter name="other"> | |
536 | <paramtype>Env &</paramtype> | |
537 | </parameter> | |
538 | <parameter name="head"> | |
539 | <paramtype><classname>proto::env</classname><Key, Value> const &</paramtype> | |
540 | </parameter> | |
541 | </signature> | |
542 | <signature> | |
543 | <template> | |
544 | <template-type-parameter name="Env"/> | |
545 | <template-type-parameter name="Key"/> | |
546 | <template-type-parameter name="Value"/> | |
547 | </template> | |
548 | <type><classname>proto::env</classname><Key, Value, <replaceable>UNCVREF</replaceable>(typename <classname>proto::result_of::as_env</classname><Env const &>::type)></type> | |
549 | <parameter name="other"> | |
550 | <paramtype>Env const &</paramtype> | |
551 | </parameter> | |
552 | <parameter name="head"> | |
553 | <paramtype><classname>proto::env</classname><Key, Value> const &</paramtype> | |
554 | </parameter> | |
555 | </signature> | |
556 | <purpose> | |
557 | For composing a larger transform environment from two smaller ones. | |
558 | </purpose> | |
559 | <description> | |
560 | <para> | |
561 | The effect of this function is to take two transform environments and compose them into | |
562 | a larger environment that contains the key/values pairs of the two. The first argument | |
563 | is allowed to not be a transform environment, in which case it is turned into one with | |
564 | the <functionname>proto::as_env()</functionname> function before composition with the | |
565 | second argument. The second argument is required to be a transform environment with exactly | |
566 | one key/value pair. | |
567 | </para> | |
568 | <para> | |
569 | <emphasis role="bold">Example:</emphasis> | |
570 | </para> | |
571 | <para> | |
572 | Given user-defined keys <code>key0</code> and <code>key1</code> of types <code>key0_type</code> | |
573 | and <code>key1_type</code>, the following code demonstrates how the chained use of <code>operator,</code> | |
574 | can build a composite transform environment containing a number of key/value pairs: | |
575 | <programlisting><classname>proto::env</classname>< | |
576 | key1_type | |
577 | , int | |
578 | , <classname>proto::env</classname>< | |
579 | key0_type | |
580 | , char const (&)[6] | |
581 | , <classname>proto::env</classname><<classname>proto::data_type</classname>, int> | |
582 | > | |
583 | > myenv = (<globalname>proto::data</globalname> = 1, key0 = "hello", key1 = 42); | |
584 | // NOTE: operator, here --^ and here --^ | |
585 | ||
586 | // Check the results: | |
587 | assert(1 == myenv[proto::data]); | |
588 | assert(0 == std::strcmp(myenv[key0], "hello")); | |
589 | assert(42 == myenv[key1]);</programlisting> | |
590 | </para> | |
591 | <para> | |
592 | <emphasis role="bold">Note:</emphasis> In the return type and the "Returns" clause, <code><replaceable>UNCVREF</replaceable>(X)</code> is | |
593 | the type <code>X</code> stripped of top-level reference and cv-qualifiers. | |
594 | </para> | |
595 | <para> | |
596 | <emphasis role="bold">Note:</emphasis> In the "Returns" clause, <code><replaceable>cv</replaceable></code> is replaced with <code>const</code> | |
597 | for the second overload, and nothing for the first. | |
598 | </para> | |
599 | <para> | |
600 | <emphasis role="bold">See also:</emphasis> | |
601 | <itemizedlist> | |
602 | <listitem> | |
603 | <code><methodname>proto::env::operator[]</methodname></code> | |
604 | </listitem> | |
605 | </itemizedlist> | |
606 | </para> | |
607 | </description> | |
608 | <returns><code><classname>proto::env</classname><Key, Value, <replaceable>UNCVREF</replaceable>(typename <classname>proto::result_of::as_env</classname><Env <replaceable>cv</replaceable> &>::type)>(head[Key()], <functionname>proto::as_env</functionname>(other))</code></returns> | |
609 | </overloaded-function> | |
610 | ||
611 | <!-- struct _env_var --> | |
612 | <struct name="_env_var"> | |
613 | <template> | |
614 | <template-type-parameter name="Key"/> | |
615 | </template> | |
616 | <purpose> | |
617 | A primitive transform that returns the value associated with a particular <code>Key</code> | |
618 | in the current transform environment. | |
619 | </purpose> | |
620 | <inherit> | |
621 | <type><classname>proto::transform</classname><_env_var<Key> ></type> | |
622 | </inherit> | |
623 | <struct name="impl"> | |
624 | <template> | |
625 | <template-type-name name="Expr"/> | |
626 | <template-type-name name="State"/> | |
627 | <template-type-name name="Data"/> | |
628 | </template> | |
629 | <inherit> | |
630 | <type><classname>proto::transform_impl</classname><Expr, State, Data> ></type> | |
631 | </inherit> | |
632 | <typedef name="result_type"> | |
633 | <type>typename <classname>proto::result_of::env_var</classname><Data, Key>::type</type> | |
634 | </typedef> | |
635 | <method-group name="public member functions"> | |
636 | <method name="operator()" cv="const"> | |
637 | <type>result_type</type> | |
638 | <parameter name=""> | |
639 | <paramtype>typename impl::expr_param</paramtype> | |
640 | </parameter> | |
641 | <parameter name=""> | |
642 | <paramtype>typename impl::state_param</paramtype> | |
643 | </parameter> | |
644 | <parameter name="data"> | |
645 | <paramtype>typename impl::data_param</paramtype> | |
646 | <description> | |
647 | <para>The current transform environment</para> | |
648 | </description> | |
649 | </parameter> | |
650 | <description> | |
651 | <para> | |
652 | Fetches the value associated with <code>Key</code> from the transform environment | |
653 | passed in the data (third) parameter. | |
654 | </para> | |
655 | </description> | |
656 | <requires> | |
657 | <para> | |
658 | <code><classname>proto::is_env</classname><Data>::value</code> | |
659 | is <code>true</code>. | |
660 | </para> | |
661 | </requires> | |
662 | <returns> | |
663 | <para> | |
664 | <code><functionname>proto::env_var</functionname>(data)</code> | |
665 | </para> | |
666 | </returns> | |
667 | </method> | |
668 | </method-group> | |
669 | </struct> | |
670 | <description> | |
671 | <para> | |
672 | See <code><classname>proto::_env_var::impl</classname></code> for the full details. | |
673 | </para> | |
674 | </description> | |
675 | </struct> | |
676 | ||
677 | <!-- struct _env --> | |
678 | <struct name="_env"> | |
679 | <purpose> | |
680 | A primitive transform that returns the current transform environment unmodified. | |
681 | </purpose> | |
682 | <inherit> | |
683 | <type><classname>proto::transform</classname><_env></type> | |
684 | </inherit> | |
685 | <struct name="impl"> | |
686 | <template> | |
687 | <template-type-name name="Expr"/> | |
688 | <template-type-name name="State"/> | |
689 | <template-type-name name="Data"/> | |
690 | </template> | |
691 | <inherit> | |
692 | <type><classname>proto::transform_impl</classname><Expr, State, Data></type> | |
693 | </inherit> | |
694 | <typedef name="result_type"> | |
695 | <type>Data</type> | |
696 | </typedef> | |
697 | <method-group name="public member functions"> | |
698 | <method name="operator()" cv="const"> | |
699 | <type>result_type</type> | |
700 | <parameter name=""> | |
701 | <paramtype>typename impl::expr_param</paramtype> | |
702 | </parameter> | |
703 | <parameter name=""> | |
704 | <paramtype>typename impl::state_param</paramtype> | |
705 | </parameter> | |
706 | <parameter name="data"> | |
707 | <paramtype>typename impl::data_param</paramtype> | |
708 | <description> | |
709 | <para>The current transform environment </para> | |
710 | </description> | |
711 | </parameter> | |
712 | <description> | |
713 | <para> | |
714 | Returns the current transform environment | |
715 | passed in the data (third) parameter. | |
716 | </para> | |
717 | </description> | |
718 | <returns> | |
719 | <para> | |
720 | <code>data</code> | |
721 | </para> | |
722 | </returns> | |
723 | </method> | |
724 | </method-group> | |
725 | </struct> | |
726 | <description> | |
727 | <para> | |
728 | See <code><classname>proto::_env::impl</classname></code> for the full details. | |
729 | </para> | |
730 | </description> | |
731 | </struct> | |
732 | </namespace> | |
733 | </namespace> | |
734 | ||
735 | <!-- BOOST_PROTO_DEFINE_ENV_VAR() --> | |
736 | <macro name="BOOST_PROTO_DEFINE_ENV_VAR" kind="functionlike"> | |
737 | <macro-parameter name="Type"/> | |
738 | <macro-parameter name="Name"/> | |
739 | <purpose> | |
740 | Define a type and a global variable of that type that can be used | |
741 | to initialize a slot in a Proto transform environment. | |
742 | </purpose> | |
743 | <description> | |
744 | <para> | |
745 | Proto primitive transforms can optionally accept an environment in | |
746 | their third parameter which is a key/value store of environment | |
747 | variables. Use the <code>BOOST_PROTO_DEFINE_ENV_VAR()</code> macro | |
748 | to define the keys. | |
749 | </para> | |
750 | <para> | |
751 | See the description for <code><classname alt="boost::proto::data_type">proto::data_type</classname></code> | |
752 | for an example of the class interface created by this macro. | |
753 | </para> | |
754 | <para> | |
755 | <emphasis role="bold">Example:</emphasis> | |
756 | </para> | |
757 | <para> | |
758 | <programlisting>BOOST_PROTO_DEFINE_ENV_VAR(mykey_type, mykey); | |
759 | ||
760 | struct FetchMyKey | |
761 | : <classname alt="boost::proto::when">proto::when</classname>< <classname alt="boost::proto::_">_</classname>, <classname alt="boost::proto::_env_var">proto::_env_var</classname><mykey_type> > | |
762 | {}; | |
763 | ||
764 | int main() | |
765 | { | |
766 | <classname alt="boost::proto::terminal">proto::terminal</classname><int>::type i = {42}; | |
767 | char const * sz = FetchMyKey()(i, 0, (mykey = "hello!")); | |
768 | assert(0 == std::strcmp(sz, "hello!"); | |
769 | }</programlisting> | |
770 | </para> | |
771 | </description> | |
772 | ||
773 | </macro> | |
774 | ||
775 | </header> |