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
|
<?xml version="1.0" encoding="utf-8"?>
<!DOCTYPE header PUBLIC "-//Boost//DTD BoostBook XML V1.0//EN"
"http://www.boost.org/tools/boostbook/dtd/boostbook.dtd">
<header name="boost/variant/apply_visitor.hpp">
<namespace name="boost">
<class name="apply_visitor_delayed_t">
<purpose>Adapts a visitor for use as a function object.</purpose>
<description>
<simpara>Adapts the function given at construction for use as a
function object. This is useful, for example, when one needs to
operate on each element of a sequence of variant objects using a
standard library algorithm such as
<code>std::for_each</code>.</simpara>
<simpara>See the "visitor-only" form of
<code><functionname>apply_visitor</functionname></code> for a simple
way to create <code>apply_visitor_delayed_t</code> objects.</simpara>
</description>
<template>
<template-type-parameter name="Visitor"/>
</template>
<typedef name="result_type">
<type>typename Visitor::result_type</type>
</typedef>
<constructor specifiers="explicit">
<parameter name="visitor">
<paramtype>Visitor &</paramtype>
</parameter>
<effects>
<simpara>Constructs the function object with the given
visitor.</simpara>
</effects>
</constructor>
<method-group name="function object interface">
<overloaded-method name="operator()">
<signature>
<template>
<template-type-parameter name="Variant"/>
</template>
<type>result_type</type>
<parameter name="operand">
<paramtype>Variant &</paramtype>
</parameter>
</signature>
<signature>
<template>
<template-type-parameter name="Variant1"/>
<template-type-parameter name="Variant2"/>
</template>
<type>result_type</type>
<parameter name="operand1">
<paramtype>Variant1 &</paramtype>
</parameter>
<parameter name="operand2">
<paramtype>Variant2 &</paramtype>
</parameter>
</signature>
<purpose>Function call operator.</purpose>
<description>
<simpara>Invokes
<code><functionname>apply_visitor</functionname></code> on the
stored visitor using the given operands.</simpara>
</description>
</overloaded-method>
</method-group>
</class>
<overloaded-function name="apply_visitor">
<signature>
<template>
<template-type-parameter name="Visitor"/>
<template-type-parameter name="Variant"/>
</template>
<type>typename Visitor::result_type</type>
<parameter name="visitor">
<paramtype>Visitor &</paramtype>
</parameter>
<parameter name="operand">
<paramtype>Variant &</paramtype>
</parameter>
</signature>
<signature>
<template>
<template-type-parameter name="Visitor"/>
<template-type-parameter name="Variant"/>
</template>
<type>typename Visitor::result_type</type>
<parameter name="visitor">
<paramtype>const Visitor &</paramtype>
</parameter>
<parameter name="operand">
<paramtype>Variant &</paramtype>
</parameter>
</signature>
<signature>
<template>
<template-type-parameter name="BinaryVisitor"/>
<template-type-parameter name="Variant1"/>
<template-type-parameter name="Variant2"/>
</template>
<type>typename BinaryVisitor::result_type</type>
<parameter name="visitor">
<paramtype>BinaryVisitor &</paramtype>
</parameter>
<parameter name="operand1">
<paramtype>Variant1 &</paramtype>
</parameter>
<parameter name="operand2">
<paramtype>Variant2 &</paramtype>
</parameter>
</signature>
<signature>
<template>
<template-type-parameter name="BinaryVisitor"/>
<template-type-parameter name="Variant1"/>
<template-type-parameter name="Variant2"/>
</template>
<type>typename BinaryVisitor::result_type</type>
<parameter name="visitor">
<paramtype>const BinaryVisitor &</paramtype>
</parameter>
<parameter name="operand1">
<paramtype>Variant1 &</paramtype>
</parameter>
<parameter name="operand2">
<paramtype>Variant2 &</paramtype>
</parameter>
</signature>
<signature>
<template>
<template-type-parameter name="Visitor"/>
</template>
<type><classname>apply_visitor_delayed_t</classname><Visitor></type>
<parameter name="visitor">
<paramtype>Visitor &</paramtype>
</parameter>
</signature>
<purpose>
<simpara>Allows compile-time checked type-safe application of the
given visitor to the content of the given variant, ensuring that all
types are handled by the visitor.</simpara>
</purpose>
<description>
<simpara>The behavior of <code>apply_visitor</code> is dependent on
the number of arguments on which it operates (i.e., other than the
visitor). The function behaves as follows:
<itemizedlist>
<listitem>Overloads accepting one operand invoke the unary function
call operator of the given visitor on the content of the given
<code><classname>variant</classname></code> operand.</listitem>
<listitem>Overloads accepting two operands invoke the binary
function call operator of the given visitor on the content of
the given <code><classname>variant</classname></code>
operands.</listitem>
<listitem>The overload accepting only a visitor returns a
<classname alt="boost::apply_visitor_delayed_t">generic function object</classname>
that accepts either one or two arguments and invokes
<code><functionname>apply_visitor</functionname></code> using
these arguments and <code>visitor</code>, thus behaving as
specified above. (This behavior is particularly useful, for
example, when one needs to operate on each element of a sequence
of variant objects using a standard library
algorithm.)</listitem>
</itemizedlist>
</simpara>
</description>
<returns>
<simpara>The overloads acccepting operands return the result of
applying the given visitor to the content of the given operands.
The overload accepting only a visitor return a function object, thus
delaying application of the visitor to any operands.</simpara>
</returns>
<requires>
<simpara>The given visitor must fulfill the
<link linkend="variant.concepts.static-visitor"><emphasis>StaticVisitor</emphasis></link>
concept requirements with respect to each of the bounded types of the
given <code>variant</code>.</simpara>
</requires>
<throws>
<simpara>The overloads accepting operands throw only if the given
visitor throws when applied. The overload accepting only a visitor
will not throw. (Note, however, that the returned
<classname alt="boost::apply_visitor_delayed_t">function object</classname>
may throw when invoked.)</simpara>
</throws>
</overloaded-function>
</namespace>
</header>
|
