1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
|
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=US-ASCII">
<title>Determine the Type of the Iterator of a Container</title>
<link rel="stylesheet" href="../../../../../../../../doc/src/boostbook.css" type="text/css">
<meta name="generator" content="DocBook XSL Stylesheets V1.76.1">
<link rel="home" href="../../../../index.html" title="Spirit 2.5.2">
<link rel="up" href="../iterate.html" title="Extract Attribute Values to Generate Output from a Container (Karma)">
<link rel="prev" href="../iterate.html" title="Extract Attribute Values to Generate Output from a Container (Karma)">
<link rel="next" href="begin_container.html" title="Get the Iterator pointing to the Begin of a Container Attribute">
</head>
<body bgcolor="white" text="black" link="#0000FF" vlink="#840084" alink="#0000FF">
<table cellpadding="2" width="100%"><tr>
<td valign="top"><img alt="Boost C++ Libraries" width="277" height="86" src="../../../../../../../../boost.png"></td>
<td align="center"><a href="../../../../../../../../index.html">Home</a></td>
<td align="center"><a href="../../../../../../../../libs/libraries.htm">Libraries</a></td>
<td align="center"><a href="http://www.boost.org/users/people.html">People</a></td>
<td align="center"><a href="http://www.boost.org/users/faq.html">FAQ</a></td>
<td align="center"><a href="../../../../../../../../more/index.htm">More</a></td>
</tr></table>
<hr>
<div class="spirit-nav">
<a accesskey="p" href="../iterate.html"><img src="../../../../../../../../doc/src/images/prev.png" alt="Prev"></a><a accesskey="u" href="../iterate.html"><img src="../../../../../../../../doc/src/images/up.png" alt="Up"></a><a accesskey="h" href="../../../../index.html"><img src="../../../../../../../../doc/src/images/home.png" alt="Home"></a><a accesskey="n" href="begin_container.html"><img src="../../../../../../../../doc/src/images/next.png" alt="Next"></a>
</div>
<div class="section">
<div class="titlepage"><div><div><h5 class="title">
<a name="spirit.advanced.customize.iterate.container_iterator"></a><a class="link" href="container_iterator.html" title="Determine the Type of the Iterator of a Container">Determine
the Type of the Iterator of a Container</a>
</h5></div></div></div>
<h6>
<a name="spirit.advanced.customize.iterate.container_iterator.h0"></a>
<span><a name="spirit.advanced.customize.iterate.container_iterator.container_iterator"></a></span><a class="link" href="container_iterator.html#spirit.advanced.customize.iterate.container_iterator.container_iterator">container_iterator</a>
</h6>
<p>
The template <code class="computeroutput"><span class="identifier">container_iterator</span></code>
is a template meta-function used as an attribute customization point.
It is invoked by the <span class="emphasis"><em>Karma</em></span> repetitive generators
(such as <a class="link" href="../../../karma/reference/operator/list.html" title="List Generator (a % b)">List (<code class="computeroutput"><span class="special">%</span></code>)</a>, <a class="link" href="../../../karma/reference/operator/kleene.html" title="Kleene Star Generator (*a)">Kleene
(unary <code class="computeroutput"><span class="special">*</span></code>)</a>, <a class="link" href="../../../karma/reference/operator/plus.html" title="Plus Generator (+a)">Plus (unary <code class="computeroutput"><span class="special">+</span></code>)</a>, and <a class="link" href="../../../karma/reference/directive/repeat.html" title="Repetition Generator Directive (repeat[])">Repeat</a>)
in order to determine the type of the iterator to use to iterate over
the items to be exposed as the elements of a container.
</p>
<h6>
<a name="spirit.advanced.customize.iterate.container_iterator.h1"></a>
<span><a name="spirit.advanced.customize.iterate.container_iterator.module_headers"></a></span><a class="link" href="container_iterator.html#spirit.advanced.customize.iterate.container_iterator.module_headers">Module
Headers</a>
</h6>
<pre class="programlisting"><span class="preprocessor">#include</span> <span class="special"><</span><span class="identifier">boost</span><span class="special">/</span><span class="identifier">spirit</span><span class="special">/</span><span class="identifier">home</span><span class="special">/</span><span class="identifier">support</span><span class="special">/</span><span class="identifier">container</span><span class="special">.</span><span class="identifier">hpp</span><span class="special">></span>
</pre>
<p>
Also, see <a class="link" href="../../../structure/include.html" title="Include">Include Structure</a>.
</p>
<div class="note"><table border="0" summary="Note">
<tr>
<td rowspan="2" align="center" valign="top" width="25"><img alt="[Note]" src="../../../../images/note.png"></td>
<th align="left">Note</th>
</tr>
<tr><td align="left" valign="top"><p>
This header file does not need to be included directly by any user
program as it is normally included by other Spirit header files relying
on its content.
</p></td></tr>
</table></div>
<h6>
<a name="spirit.advanced.customize.iterate.container_iterator.h2"></a>
<span><a name="spirit.advanced.customize.iterate.container_iterator.namespace"></a></span><a class="link" href="container_iterator.html#spirit.advanced.customize.iterate.container_iterator.namespace">Namespace</a>
</h6>
<div class="informaltable"><table class="table">
<colgroup><col></colgroup>
<thead><tr><th>
<p>
Name
</p>
</th></tr></thead>
<tbody><tr><td>
<p>
<code class="computeroutput"><span class="identifier">boost</span><span class="special">::</span><span class="identifier">spirit</span><span class="special">::</span><span class="identifier">traits</span></code>
</p>
</td></tr></tbody>
</table></div>
<h6>
<a name="spirit.advanced.customize.iterate.container_iterator.h3"></a>
<span><a name="spirit.advanced.customize.iterate.container_iterator.synopsis"></a></span><a class="link" href="container_iterator.html#spirit.advanced.customize.iterate.container_iterator.synopsis">Synopsis</a>
</h6>
<pre class="programlisting"><span class="keyword">template</span> <span class="special"><</span><span class="keyword">typename</span> <span class="identifier">Container</span><span class="special">,</span> <span class="keyword">typename</span> <span class="identifier">Enable</span><span class="special">></span>
<span class="keyword">struct</span> <span class="identifier">container_iterator</span>
<span class="special">{</span>
<span class="keyword">typedef</span> <span class="special"><</span><span class="identifier">unspecified</span><span class="special">></span> <span class="identifier">type</span><span class="special">;</span>
<span class="special">};</span>
</pre>
<h6>
<a name="spirit.advanced.customize.iterate.container_iterator.h4"></a>
<span><a name="spirit.advanced.customize.iterate.container_iterator.template_parameters"></a></span><a class="link" href="container_iterator.html#spirit.advanced.customize.iterate.container_iterator.template_parameters">Template
parameters</a>
</h6>
<div class="informaltable"><table class="table">
<colgroup>
<col>
<col>
<col>
</colgroup>
<thead><tr>
<th>
<p>
Parameter
</p>
</th>
<th>
<p>
Description
</p>
</th>
<th>
<p>
Default
</p>
</th>
</tr></thead>
<tbody>
<tr>
<td>
<p>
<code class="computeroutput"><span class="identifier">Container</span></code>
</p>
</td>
<td>
<p>
The type, <code class="computeroutput"><span class="identifier">Container</span></code>
for which the iterator type has to be returned
</p>
</td>
<td>
<p>
none
</p>
</td>
</tr>
<tr>
<td>
<p>
<code class="computeroutput"><span class="identifier">Enable</span></code>
</p>
</td>
<td>
<p>
Helper template parameter usable to selectively enable or disable
certain specializations of <code class="computeroutput"><span class="identifier">container_iterator</span></code>
utilizing SFINAE (i.e. <code class="computeroutput"><span class="identifier">boost</span><span class="special">::</span><span class="identifier">enable_if</span></code>
or <code class="computeroutput"><span class="identifier">boost</span><span class="special">::</span><span class="identifier">disable_if</span></code>).
</p>
</td>
<td>
<p>
<code class="computeroutput"><span class="keyword">void</span></code>
</p>
</td>
</tr>
</tbody>
</table></div>
<div class="variablelist">
<p class="title"><b>Notation</b></p>
<dl>
<dt><span class="term"><code class="computeroutput"><span class="identifier">C</span></code></span></dt>
<dd><p>
A container type the iterator type needs to be evaluated for.
</p></dd>
</dl>
</div>
<h6>
<a name="spirit.advanced.customize.iterate.container_iterator.h5"></a>
<span><a name="spirit.advanced.customize.iterate.container_iterator.expression_semantics"></a></span><a class="link" href="container_iterator.html#spirit.advanced.customize.iterate.container_iterator.expression_semantics">Expression
Semantics</a>
</h6>
<div class="informaltable"><table class="table">
<colgroup>
<col>
<col>
</colgroup>
<thead><tr>
<th>
<p>
Expression
</p>
</th>
<th>
<p>
Semantics
</p>
</th>
</tr></thead>
<tbody><tr>
<td>
<p>
<code class="computeroutput"><span class="identifier">container_iterator</span><span class="special"><</span><span class="identifier">C</span><span class="special">>::</span><span class="identifier">type</span></code>
</p>
</td>
<td>
<p>
Result of the metafunction that evaluates the type to be used
as the iterator for accessing all elements of a container,
<code class="computeroutput"><span class="identifier">C</span></code>.
</p>
</td>
</tr></tbody>
</table></div>
<p>
The returned type conceptually needs to be equivalent to a standard forward
iterator. But it does not have to expose the standardized interface.
If this customization point is implemented for a certain container type,
all related customization points need to be implemented as well (see
<a class="link" href="container_iterator.html#spirit.advanced.customize.iterate.container_iterator.related_attribute_customization_points">Related
Attribute Customization Points</a> below). This encapsulates the specific
iterator interface required for a given type. The minimal requirements
for a type to be exposed as an iterator in this context are:
</p>
<div class="itemizedlist"><ul class="itemizedlist" type="disc">
<li class="listitem">
it needs to be comparable for equality (see <a class="link" href="compare_iterators.html" title="Compare two Iterator pointing into a Container Attribute for Equality"><code class="computeroutput"><span class="identifier">traits</span><span class="special">::</span><span class="identifier">compare_iterators</span></code></a>),
</li>
<li class="listitem">
it needs to be incrementable (see <a class="link" href="next_iterator.html" title="Increment the Iterator pointing into a Container Attribute"><code class="computeroutput"><span class="identifier">traits</span><span class="special">::</span><span class="identifier">next_iterator</span></code></a>),
</li>
<li class="listitem">
it needs to be dereferencible (see <a class="link" href="deref_iterator.html" title="Dereference the Iterator pointing into a Container Attribute"><code class="computeroutput"><span class="identifier">traits</span><span class="special">::</span><span class="identifier">deref_iterator</span></code></a>).
</li>
</ul></div>
<h6>
<a name="spirit.advanced.customize.iterate.container_iterator.h6"></a>
<span><a name="spirit.advanced.customize.iterate.container_iterator.predefined_specializations"></a></span><a class="link" href="container_iterator.html#spirit.advanced.customize.iterate.container_iterator.predefined_specializations">Predefined
Specializations</a>
</h6>
<p>
<a href="http://boost-spirit.com" target="_top">Spirit</a> predefines specializations
of this customization point for several types. The following table lists
those types together with the types returned by the embedded typedef
<code class="computeroutput"><span class="identifier">type</span></code>:
</p>
<div class="informaltable"><table class="table">
<colgroup>
<col>
<col>
</colgroup>
<thead><tr>
<th>
<p>
Template Parameters
</p>
</th>
<th>
<p>
Semantics
</p>
</th>
</tr></thead>
<tbody>
<tr>
<td>
<p>
<code class="computeroutput"><span class="identifier">C</span></code>
</p>
</td>
<td>
<p>
Returns <code class="computeroutput"><span class="identifier">C</span><span class="special">::</span><span class="identifier">iterator</span></code>.
</p>
</td>
</tr>
<tr>
<td>
<p>
<code class="computeroutput"><span class="identifier">C</span> <span class="keyword">const</span></code>
</p>
</td>
<td>
<p>
Returns <code class="computeroutput"><span class="identifier">C</span><span class="special">::</span><span class="identifier">const_iterator</span></code>.
</p>
</td>
</tr>
<tr>
<td>
<p>
<code class="computeroutput"><span class="identifier">unused_type</span></code>
</p>
</td>
<td>
<p>
Returns <code class="computeroutput"><span class="identifier">unused_type</span></code><code class="computeroutput">
<span class="keyword">const</span><span class="special">*</span></code>.
</p>
</td>
</tr>
</tbody>
</table></div>
<h6>
<a name="spirit.advanced.customize.iterate.container_iterator.h7"></a>
<span><a name="spirit.advanced.customize.iterate.container_iterator.when_to_implement"></a></span><a class="link" href="container_iterator.html#spirit.advanced.customize.iterate.container_iterator.when_to_implement">When
to implement</a>
</h6>
<p>
The customization point <code class="computeroutput"><span class="identifier">container_iterator</span></code>
needs to be implemented for a specific type whenever this type is to
be used as an attribute in place of a STL container. It is applicable
for generators (<span class="emphasis"><em>Spirit.Karma</em></span>) only. As a rule of
thumb: it has to be implemented whenever a certain type is to be passed
as an attribute to a generator normally exposing a STL container, <code class="computeroutput"><span class="identifier">C</span></code> and if the type does not expose the
interface of a STL container (i.e. <code class="computeroutput"><span class="identifier">is_container</span><span class="special"><</span><span class="identifier">C</span><span class="special">>::</span><span class="identifier">type</span></code>
would normally return <code class="computeroutput"><span class="identifier">mpl</span><span class="special">::</span><span class="identifier">false_</span></code>).
</p>
<h6>
<a name="spirit.advanced.customize.iterate.container_iterator.h8"></a>
<span><a name="spirit.advanced.customize.iterate.container_iterator.related_attribute_customization_points"></a></span><a class="link" href="container_iterator.html#spirit.advanced.customize.iterate.container_iterator.related_attribute_customization_points">Related
Attribute Customization Points</a>
</h6>
<p>
If this customization point is implemented, the following other customization
points might need to be implemented as well.
</p>
<div class="informaltable"><table class="table">
<colgroup>
<col>
<col>
</colgroup>
<thead><tr>
<th>
<p>
Name
</p>
</th>
<th>
<p>
When to implement
</p>
</th>
</tr></thead>
<tbody>
<tr>
<td>
<p>
<a class="link" href="../is_container.html" title="Determine if a Type Should be Treated as a Container (Qi and Karma)"><code class="computeroutput"><span class="identifier">traits</span><span class="special">::</span><span class="identifier">is_container</span></code></a>
</p>
</td>
<td>
<p>
Needs to be implemented whenever a type is to be used as a
container attribute in <span class="emphasis"><em>Karma</em></span>.
</p>
</td>
</tr>
<tr>
<td>
<p>
<a class="link" href="container_iterator.html" title="Determine the Type of the Iterator of a Container"><code class="computeroutput"><span class="identifier">traits</span><span class="special">::</span><span class="identifier">container_iterator</span></code></a>
</p>
</td>
<td>
<p>
Karma: <a class="link" href="../../../karma/reference/operator/list.html" title="List Generator (a % b)">List
(<code class="computeroutput"><span class="special">%</span></code>)</a>, <a class="link" href="../../../karma/reference/operator/kleene.html" title="Kleene Star Generator (*a)">Kleene (unary
<code class="computeroutput"><span class="special">*</span></code>)</a>, <a class="link" href="../../../karma/reference/operator/plus.html" title="Plus Generator (+a)">Plus (unary
<code class="computeroutput"><span class="special">+</span></code>)</a>, <a class="link" href="../../../karma/reference/directive/repeat.html" title="Repetition Generator Directive (repeat[])">Repeat</a>.
</p>
</td>
</tr>
<tr>
<td>
<p>
<a class="link" href="begin_container.html" title="Get the Iterator pointing to the Begin of a Container Attribute"><code class="computeroutput"><span class="identifier">traits</span><span class="special">::</span><span class="identifier">begin_container</span></code></a>
</p>
</td>
<td>
<p>
Karma: <a class="link" href="../../../karma/reference/operator/list.html" title="List Generator (a % b)">List
(<code class="computeroutput"><span class="special">%</span></code>)</a>, <a class="link" href="../../../karma/reference/operator/kleene.html" title="Kleene Star Generator (*a)">Kleene (unary
<code class="computeroutput"><span class="special">*</span></code>)</a>, <a class="link" href="../../../karma/reference/operator/plus.html" title="Plus Generator (+a)">Plus (unary
<code class="computeroutput"><span class="special">+</span></code>)</a>, <a class="link" href="../../../karma/reference/directive/repeat.html" title="Repetition Generator Directive (repeat[])">Repeat</a>.
</p>
</td>
</tr>
<tr>
<td>
<p>
<a class="link" href="end_container.html" title="Get the Iterator pointing to the End of a Container Attribute"><code class="computeroutput"><span class="identifier">traits</span><span class="special">::</span><span class="identifier">end_container</span></code></a>
</p>
</td>
<td>
<p>
Karma: <a class="link" href="../../../karma/reference/operator/list.html" title="List Generator (a % b)">List
(<code class="computeroutput"><span class="special">%</span></code>)</a>, <a class="link" href="../../../karma/reference/operator/kleene.html" title="Kleene Star Generator (*a)">Kleene (unary
<code class="computeroutput"><span class="special">*</span></code>)</a>, <a class="link" href="../../../karma/reference/operator/plus.html" title="Plus Generator (+a)">Plus (unary
<code class="computeroutput"><span class="special">+</span></code>)</a>, <a class="link" href="../../../karma/reference/directive/repeat.html" title="Repetition Generator Directive (repeat[])">Repeat</a>.
</p>
</td>
</tr>
<tr>
<td>
<p>
<a class="link" href="deref_iterator.html" title="Dereference the Iterator pointing into a Container Attribute"><code class="computeroutput"><span class="identifier">traits</span><span class="special">::</span><span class="identifier">deref_iterator</span></code></a>
</p>
</td>
<td>
<p>
Karma: <a class="link" href="../../../karma/reference/operator/list.html" title="List Generator (a % b)">List
(<code class="computeroutput"><span class="special">%</span></code>)</a>, <a class="link" href="../../../karma/reference/operator/kleene.html" title="Kleene Star Generator (*a)">Kleene (unary
<code class="computeroutput"><span class="special">*</span></code>)</a>, <a class="link" href="../../../karma/reference/operator/plus.html" title="Plus Generator (+a)">Plus (unary
<code class="computeroutput"><span class="special">+</span></code>)</a>, <a class="link" href="../../../karma/reference/directive/repeat.html" title="Repetition Generator Directive (repeat[])">Repeat</a>.
</p>
</td>
</tr>
<tr>
<td>
<p>
<a class="link" href="next_iterator.html" title="Increment the Iterator pointing into a Container Attribute"><code class="computeroutput"><span class="identifier">traits</span><span class="special">::</span><span class="identifier">next_iterator</span></code></a>
</p>
</td>
<td>
<p>
Karma: <a class="link" href="../../../karma/reference/operator/list.html" title="List Generator (a % b)">List
(<code class="computeroutput"><span class="special">%</span></code>)</a>, <a class="link" href="../../../karma/reference/operator/kleene.html" title="Kleene Star Generator (*a)">Kleene (unary
<code class="computeroutput"><span class="special">*</span></code>)</a>, <a class="link" href="../../../karma/reference/operator/plus.html" title="Plus Generator (+a)">Plus (unary
<code class="computeroutput"><span class="special">+</span></code>)</a>, <a class="link" href="../../../karma/reference/directive/repeat.html" title="Repetition Generator Directive (repeat[])">Repeat</a>.
</p>
</td>
</tr>
<tr>
<td>
<p>
<a class="link" href="compare_iterators.html" title="Compare two Iterator pointing into a Container Attribute for Equality"><code class="computeroutput"><span class="identifier">traits</span><span class="special">::</span><span class="identifier">compare_iterators</span></code></a>
</p>
</td>
<td>
<p>
Karma: <a class="link" href="../../../karma/reference/operator/list.html" title="List Generator (a % b)">List
(<code class="computeroutput"><span class="special">%</span></code>)</a>, <a class="link" href="../../../karma/reference/operator/kleene.html" title="Kleene Star Generator (*a)">Kleene (unary
<code class="computeroutput"><span class="special">*</span></code>)</a>, <a class="link" href="../../../karma/reference/operator/plus.html" title="Plus Generator (+a)">Plus (unary
<code class="computeroutput"><span class="special">+</span></code>)</a>, <a class="link" href="../../../karma/reference/directive/repeat.html" title="Repetition Generator Directive (repeat[])">Repeat</a>.
</p>
</td>
</tr>
</tbody>
</table></div>
<h6>
<a name="spirit.advanced.customize.iterate.container_iterator.h9"></a>
<span><a name="spirit.advanced.customize.iterate.container_iterator.example"></a></span><a class="link" href="container_iterator.html#spirit.advanced.customize.iterate.container_iterator.example">Example</a>
</h6>
<p>
Here are the header files needed to make the example code below compile:
</p>
<p>
</p>
<pre class="programlisting"><span class="preprocessor">#include</span> <span class="special"><</span><span class="identifier">boost</span><span class="special">/</span><span class="identifier">spirit</span><span class="special">/</span><span class="identifier">include</span><span class="special">/</span><span class="identifier">karma</span><span class="special">.</span><span class="identifier">hpp</span><span class="special">></span>
<span class="preprocessor">#include</span> <span class="special"><</span><span class="identifier">iostream</span><span class="special">></span>
<span class="preprocessor">#include</span> <span class="special"><</span><span class="identifier">vector</span><span class="special">></span>
</pre>
<p>
</p>
<p>
The example (for the full source code please see here: <a href="../../../../../../example/karma/customize_embedded_container.cpp" target="_top">customize_embedded_container.cpp</a>)
uses the data structure
</p>
<p>
</p>
<pre class="programlisting"><span class="keyword">namespace</span> <span class="identifier">client</span>
<span class="special">{</span>
<span class="keyword">struct</span> <span class="identifier">embedded_container</span>
<span class="special">{</span>
<span class="comment">// expose the iterator of the embedded vector as our iterator</span>
<span class="keyword">typedef</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">vector</span><span class="special"><</span><span class="keyword">int</span><span class="special">>::</span><span class="identifier">const_iterator</span> <span class="identifier">iterator</span><span class="special">;</span>
<span class="comment">// expose the type of the held data elements as our type</span>
<span class="keyword">typedef</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">vector</span><span class="special"><</span><span class="keyword">int</span><span class="special">>::</span><span class="identifier">value_type</span> <span class="identifier">type</span><span class="special">;</span>
<span class="comment">// this is the vector holding the actual elements we need to generate </span>
<span class="comment">// output from</span>
<span class="identifier">std</span><span class="special">::</span><span class="identifier">vector</span><span class="special"><</span><span class="keyword">int</span><span class="special">></span> <span class="identifier">data</span><span class="special">;</span>
<span class="special">};</span>
<span class="special">}</span>
</pre>
<p>
</p>
<p>
as a direct container attribute to the <a class="link" href="../../../karma/reference/operator/list.html" title="List Generator (a % b)">List
(<code class="computeroutput"><span class="special">%</span></code>)</a> generator. In
order to make this data structure compatible we need to specialize a
couple of attribute customization points: <a class="link" href="../is_container.html" title="Determine if a Type Should be Treated as a Container (Qi and Karma)"><code class="computeroutput"><span class="identifier">traits</span><span class="special">::</span><span class="identifier">is_container</span></code></a>, <a class="link" href="container_iterator.html" title="Determine the Type of the Iterator of a Container"><code class="computeroutput"><span class="identifier">traits</span><span class="special">::</span><span class="identifier">container_iterator</span></code></a>, <a class="link" href="begin_container.html" title="Get the Iterator pointing to the Begin of a Container Attribute"><code class="computeroutput"><span class="identifier">traits</span><span class="special">::</span><span class="identifier">begin_container</span></code></a>, and <a class="link" href="end_container.html" title="Get the Iterator pointing to the End of a Container Attribute"><code class="computeroutput"><span class="identifier">traits</span><span class="special">::</span><span class="identifier">end_container</span></code></a>. As you can see
the specializations simply expose the embedded <code class="computeroutput"><span class="identifier">std</span><span class="special">::</span><span class="identifier">vector</span><span class="special"><</span><span class="keyword">int</span><span class="special">></span></code> as the container to use. We don't
need to specialize the customization points related to iterators (<a class="link" href="deref_iterator.html" title="Dereference the Iterator pointing into a Container Attribute"><code class="computeroutput"><span class="identifier">traits</span><span class="special">::</span><span class="identifier">deref_iterator</span></code></a>, <a class="link" href="next_iterator.html" title="Increment the Iterator pointing into a Container Attribute"><code class="computeroutput"><span class="identifier">traits</span><span class="special">::</span><span class="identifier">next_iterator</span></code></a>, and <a class="link" href="compare_iterators.html" title="Compare two Iterator pointing into a Container Attribute for Equality"><code class="computeroutput"><span class="identifier">traits</span><span class="special">::</span><span class="identifier">compare_iterators</span></code></a>) as we expose
a standard iterator and the default implementation of these customizations
handles standard iterators out of the box.
</p>
<p>
</p>
<pre class="programlisting"><span class="comment">// All specializations of attribute customization points have to be placed into</span>
<span class="comment">// the namespace boost::spirit::traits.</span>
<span class="comment">//</span>
<span class="comment">// Note that all templates below are specialized using the 'const' type.</span>
<span class="comment">// This is necessary as all attributes in Karma are 'const'.</span>
<span class="keyword">namespace</span> <span class="identifier">boost</span> <span class="special">{</span> <span class="keyword">namespace</span> <span class="identifier">spirit</span> <span class="special">{</span> <span class="keyword">namespace</span> <span class="identifier">traits</span>
<span class="special">{</span>
<span class="comment">// The specialization of the template 'is_container<>' will tell the </span>
<span class="comment">// library to treat the type 'client::embedded_container' as a </span>
<span class="comment">// container holding the items to generate output from.</span>
<span class="keyword">template</span> <span class="special"><></span>
<span class="keyword">struct</span> <span class="identifier">is_container</span><span class="special"><</span><span class="identifier">client</span><span class="special">::</span><span class="identifier">embedded_container</span> <span class="keyword">const</span><span class="special">></span>
<span class="special">:</span> <span class="identifier">mpl</span><span class="special">::</span><span class="identifier">true_</span>
<span class="special">{};</span>
<span class="comment">// The specialization of the template 'container_iterator<>' will be</span>
<span class="comment">// invoked by the library to evaluate the iterator type to be used</span>
<span class="comment">// for iterating the data elements in the container. We simply return</span>
<span class="comment">// the type of the iterator exposed by the embedded 'std::vector<int>'.</span>
<span class="keyword">template</span> <span class="special"><></span>
<span class="keyword">struct</span> <span class="identifier">container_iterator</span><span class="special"><</span><span class="identifier">client</span><span class="special">::</span><span class="identifier">embedded_container</span> <span class="keyword">const</span><span class="special">></span>
<span class="special">{</span>
<span class="keyword">typedef</span> <span class="identifier">client</span><span class="special">::</span><span class="identifier">embedded_container</span><span class="special">::</span><span class="identifier">iterator</span> <span class="identifier">type</span><span class="special">;</span>
<span class="special">};</span>
<span class="comment">// The specialization of the templates 'begin_container<>' and </span>
<span class="comment">// 'end_container<>' below will be used by the library to get the iterators </span>
<span class="comment">// pointing to the begin and the end of the data to generate output from. </span>
<span class="comment">// These specializations simply return the 'begin' and 'end' iterators as </span>
<span class="comment">// exposed by the embedded 'std::vector<int>'.</span>
<span class="comment">//</span>
<span class="comment">// The passed argument refers to the attribute instance passed to the list </span>
<span class="comment">// generator.</span>
<span class="keyword">template</span> <span class="special"><></span>
<span class="keyword">struct</span> <span class="identifier">begin_container</span><span class="special"><</span><span class="identifier">client</span><span class="special">::</span><span class="identifier">embedded_container</span> <span class="keyword">const</span><span class="special">></span>
<span class="special">{</span>
<span class="keyword">static</span> <span class="identifier">client</span><span class="special">::</span><span class="identifier">embedded_container</span><span class="special">::</span><span class="identifier">iterator</span>
<span class="identifier">call</span><span class="special">(</span><span class="identifier">client</span><span class="special">::</span><span class="identifier">embedded_container</span> <span class="keyword">const</span><span class="special">&</span> <span class="identifier">d</span><span class="special">)</span>
<span class="special">{</span>
<span class="keyword">return</span> <span class="identifier">d</span><span class="special">.</span><span class="identifier">data</span><span class="special">.</span><span class="identifier">begin</span><span class="special">();</span>
<span class="special">}</span>
<span class="special">};</span>
<span class="keyword">template</span> <span class="special"><></span>
<span class="keyword">struct</span> <span class="identifier">end_container</span><span class="special"><</span><span class="identifier">client</span><span class="special">::</span><span class="identifier">embedded_container</span> <span class="keyword">const</span><span class="special">></span>
<span class="special">{</span>
<span class="keyword">static</span> <span class="identifier">client</span><span class="special">::</span><span class="identifier">embedded_container</span><span class="special">::</span><span class="identifier">iterator</span>
<span class="identifier">call</span><span class="special">(</span><span class="identifier">client</span><span class="special">::</span><span class="identifier">embedded_container</span> <span class="keyword">const</span><span class="special">&</span> <span class="identifier">d</span><span class="special">)</span>
<span class="special">{</span>
<span class="keyword">return</span> <span class="identifier">d</span><span class="special">.</span><span class="identifier">data</span><span class="special">.</span><span class="identifier">end</span><span class="special">();</span>
<span class="special">}</span>
<span class="special">};</span>
<span class="special">}}}</span>
</pre>
<p>
</p>
<p>
The last code snippet shows an example using an instance of the data
structure <code class="computeroutput"><span class="identifier">client</span><span class="special">::</span><span class="identifier">embedded_container</span></code> to generate output
from a <a class="link" href="../../../karma/reference/operator/list.html" title="List Generator (a % b)">List (<code class="computeroutput"><span class="special">%</span></code>)</a> generator:
</p>
<p>
</p>
<pre class="programlisting"><span class="identifier">client</span><span class="special">::</span><span class="identifier">embedded_container</span> <span class="identifier">d1</span><span class="special">;</span> <span class="comment">// create some test data</span>
<span class="identifier">d1</span><span class="special">.</span><span class="identifier">data</span><span class="special">.</span><span class="identifier">push_back</span><span class="special">(</span><span class="number">1</span><span class="special">);</span>
<span class="identifier">d1</span><span class="special">.</span><span class="identifier">data</span><span class="special">.</span><span class="identifier">push_back</span><span class="special">(</span><span class="number">2</span><span class="special">);</span>
<span class="identifier">d1</span><span class="special">.</span><span class="identifier">data</span><span class="special">.</span><span class="identifier">push_back</span><span class="special">(</span><span class="number">3</span><span class="special">);</span>
<span class="comment">// use the instance of an 'client::embedded_container' instead of a </span>
<span class="comment">// STL vector</span>
<span class="identifier">std</span><span class="special">::</span><span class="identifier">cout</span> <span class="special"><<</span> <span class="identifier">karma</span><span class="special">::</span><span class="identifier">format</span><span class="special">(</span><span class="identifier">karma</span><span class="special">::</span><span class="identifier">int_</span> <span class="special">%</span> <span class="string">", "</span><span class="special">,</span> <span class="identifier">d1</span><span class="special">)</span> <span class="special"><<</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">endl</span><span class="special">;</span> <span class="comment">// prints: '1, 2, 3'</span>
</pre>
<p>
</p>
<p>
As you can see, the specializations for the customization points as defined
above enable the seamless integration of the custom data structure without
having to modify the output format or the generator itself.
</p>
<p>
For other examples of how to use the customization point <code class="computeroutput"><span class="identifier">container_iterator</span></code> please see here:
<a class="link" href="next_iterator.html#spirit.advanced.customize.iterate.next_iterator.example">use_as_container</a>
and <a class="link" href="deref_iterator.html#spirit.advanced.customize.iterate.deref_iterator.example">counter_example</a>.
</p>
</div>
<table xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" width="100%"><tr>
<td align="left"></td>
<td align="right"><div class="copyright-footer">Copyright © 2001-2011 Joel de Guzman, Hartmut Kaiser<p>
Distributed under the Boost Software License, Version 1.0. (See accompanying
file LICENSE_1_0.txt or copy at <a href="http://www.boost.org/LICENSE_1_0.txt" target="_top">http://www.boost.org/LICENSE_1_0.txt</a>)
</p>
</div></td>
</tr></table>
<hr>
<div class="spirit-nav">
<a accesskey="p" href="../iterate.html"><img src="../../../../../../../../doc/src/images/prev.png" alt="Prev"></a><a accesskey="u" href="../iterate.html"><img src="../../../../../../../../doc/src/images/up.png" alt="Up"></a><a accesskey="h" href="../../../../index.html"><img src="../../../../../../../../doc/src/images/home.png" alt="Home"></a><a accesskey="n" href="begin_container.html"><img src="../../../../../../../../doc/src/images/next.png" alt="Next"></a>
</div>
</body>
</html>
|
