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
|
<?xml version="1.0" encoding="utf-8"?>
<!--
Copyright 2012 Eric Niebler
Distributed under the Boost
Software License, Version 1.0. (See accompanying
file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
-->
<header name="boost/proto/transform/lazy.hpp">
<para>
Contains definition of the
<computeroutput>
<classname alt="boost::proto::lazy">proto::lazy<></classname>
</computeroutput> transform.
</para>
<namespace name="boost">
<namespace name="proto">
<struct name="lazy">
<template>
<template-type-parameter name="T"/>
</template>
<inherit><classname>proto::transform</classname>< lazy<T> ></inherit>
<purpose>A <conceptname>PrimitiveTransform</conceptname> that uses
<computeroutput><classname>proto::make<></classname></computeroutput> to build a
<conceptname>CallableTransform</conceptname>, and then uses
<computeroutput><classname>proto::call<></classname></computeroutput> to apply it.
</purpose>
<description>
<para>
<computeroutput>proto::lazy<></computeroutput> is useful as a higher-order transform,
when the transform to be applied depends on the current state of the transformation. The
invocation of the <computeroutput>
<classname>proto::make<></classname>
</computeroutput> transform evaluates any nested transforms, and the resulting type is treated
as a <conceptname>CallableTransform</conceptname>, which is evaluated with
<computeroutput><classname>proto::call<></classname></computeroutput>.
</para>
<para>
For the full description of the behavior of the
<computeroutput>
<classname>proto::lazy<></classname>
</computeroutput>
transform, see the documentation for the nested
<computeroutput>
<classname>proto::lazy::impl<></classname>
</computeroutput>
class template.
</para>
</description>
<struct name="impl">
<template>
<template-type-parameter name="Expr"/>
<template-type-parameter name="State"/>
<template-type-parameter name="Data"/>
</template>
<inherit><type><classname>proto::transform_impl</classname><Expr, State, Data></type></inherit>
<typedef name="result_type">
<type><replaceable>see-below</replaceable></type>
<description>
<para>
<computeroutput><classname>proto::lazy</classname><T>::impl<Expr,State,Data>::result_type</computeroutput>
is calculated as follows:
<itemizedlist>
<listitem>
<para>
If <computeroutput>T</computeroutput> if of the form
<computeroutput>O(A<subscript>0</subscript>,…A<subscript>n</subscript>)</computeroutput>, then let <computeroutput>O'</computeroutput>
be <computeroutput>boost::result_of<<classname>proto::make</classname><O>(Expr, State, Data)>::type</computeroutput>
and let <computeroutput>T'</computeroutput> be <computeroutput>O'(A<subscript>0</subscript>,…A<subscript>n</subscript>)</computeroutput>.
</para>
</listitem>
<listitem>
<para>
If <computeroutput>T</computeroutput> if of the form
<computeroutput>O(A<subscript>0</subscript>,…A<subscript>n</subscript> ...)</computeroutput>, then let <computeroutput>O'</computeroutput>
be <computeroutput>boost::result_of<<classname>proto::make</classname><O>(Expr, State, Data)>::type</computeroutput>
and let <computeroutput>T'</computeroutput> be <computeroutput>O'(A<subscript>0</subscript>,…A<subscript>n</subscript> ...)</computeroutput>.
</para>
</listitem>
<listitem>
<para>
Otherwise, let <computeroutput>T'</computeroutput>
be <computeroutput>boost::result_of<<classname>proto::make</classname><T>(Expr, State, Data)>::type</computeroutput>.
</para>
</listitem>
</itemizedlist>
<para>
The result type is
<computeroutput>
boost::result_of<<classname>proto::call</classname><T'>(Expr, State, Data)>::type
</computeroutput>.
</para>
</para>
</description>
</typedef>
<method-group name="public member functions">
<method name="operator()" cv="const">
<type>result_type</type>
<parameter name="expr">
<paramtype>typename impl::expr_param</paramtype>
</parameter>
<parameter name="state">
<paramtype>typename impl::state_param</paramtype>
</parameter>
<parameter name="data">
<paramtype>typename impl::data_param</paramtype>
</parameter>
<description>
<para>
<computeroutput><classname>proto::lazy</classname><T>::impl<Expr,State,Data>::operator()</computeroutput> behaves as follows:
<itemizedlist>
<listitem>
<para>
If <computeroutput>T</computeroutput> if of the form
<computeroutput>O(A<subscript>0</subscript>,…A<subscript>n</subscript>)</computeroutput>, then let <computeroutput>O'</computeroutput>
be <computeroutput>boost::result_of<<classname>proto::make</classname><O>(Expr, State, Data)>::type</computeroutput>
and let <computeroutput>T'</computeroutput> be <computeroutput>O'(A<subscript>0</subscript>,…A<subscript>n</subscript>)</computeroutput>.
</para>
</listitem>
<listitem>
<para>
If <computeroutput>T</computeroutput> if of the form
<computeroutput>O(A<subscript>0</subscript>,…A<subscript>n</subscript> ...)</computeroutput>, then let <computeroutput>O'</computeroutput>
be <computeroutput>boost::result_of<<classname>proto::make</classname><O>(Expr, State, Data)>::type</computeroutput>
and let <computeroutput>T'</computeroutput> be <computeroutput>O'(A<subscript>0</subscript>,…A<subscript>n</subscript> ...)</computeroutput>.
</para>
</listitem>
<listitem>
<para>
Otherwise, let <computeroutput>T'</computeroutput>
be <computeroutput>boost::result_of<<classname>proto::make</classname><T>(Expr, State, Data)>::type</computeroutput>.
</para>
</listitem>
</itemizedlist>
</para>
</description>
<returns>
<para>
<computeroutput>
<classname>proto::call</classname><T'>()(expr, state, data)
</computeroutput>
</para>
</returns>
</method>
</method-group>
</struct>
</struct>
</namespace>
</namespace>
</header>
|
