tclap 1.2.5
ArgTraits.h
Go to the documentation of this file.
1// -*- Mode: c++; c-basic-offset: 4; tab-width: 4; -*-
2
3/******************************************************************************
4 *
5 * file: ArgTraits.h
6 *
7 * Copyright (c) 2007, Daniel Aarno, Michael E. Smoot .
8 * Copyright (c) 2017 Google LLC
9 * All rights reserved.
10 *
11 * See the file COPYING in the top directory of this distribution for
12 * more information.
13 *
14 * THE SOFTWARE IS PROVIDED _AS IS_, WITHOUT WARRANTY OF ANY KIND, EXPRESS
15 * OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
16 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
17 * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
18 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
19 * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
20 * DEALINGS IN THE SOFTWARE.
21 *
22 *****************************************************************************/
23
24// This is an internal tclap file, you should probably not have to
25// include this directly
26
27#ifndef TCLAP_ARGTRAITS_H
28#define TCLAP_ARGTRAITS_H
29
30namespace TCLAP {
31
32// We use two empty structs to get compile type specialization
33// function to work
34
39struct ValueLike {
41 virtual ~ValueLike() {}
42};
43
49struct StringLike {
50 virtual ~StringLike() {}
51};
52
62
70 virtual ~ValueLikeTrait() {}
71};
72
81template<typename T>
82class ArgTraits {
83 // This is a bit silly, but what we want to do is:
84 // 1) If there exists a specialization of ArgTraits for type X,
85 // use it.
86 //
87 // 2) If no specialization exists but X has the typename
88 // X::ValueCategory, use the specialization for X::ValueCategory.
89 //
90 // 3) If neither (1) nor (2) defines the trait, use the default
91 // which is ValueLike.
92
93 // This is the "how":
94 //
95 // test<T>(0) (where 0 is the NULL ptr) will match
96 // test(typename C::ValueCategory*) iff type T has the
97 // corresponding typedef. If it does not test(...) will be
98 // matched. This allows us to determine if T::ValueCategory
99 // exists by checking the sizeof for the test function (return
100 // value must have different sizeof).
101 template<typename C> static short test(typename C::ValueCategory*);
102 template<typename C> static long test(...);
103 static const bool hasTrait = sizeof(test<T>(0)) == sizeof(short);
104
105 template <typename C, bool>
106 struct DefaultArgTrait {
107 typedef ValueLike ValueCategory;
108 };
109
110 template <typename C>
111 struct DefaultArgTrait<C, true> {
112 typedef typename C::ValueCategory ValueCategory;
113 };
114
115public:
117};
118
119} // namespace
120
121#endif
122
Arg traits are used to get compile type specialization when parsing argument values.
Definition ArgTraits.h:82
DefaultArgTrait< T, hasTrait >::ValueCategory ValueCategory
Definition ArgTraits.h:116
Definition Arg.h:48
A class can inherit from this object to make it have string like traits.
Definition ArgTraits.h:58
StringLike ValueCategory
Definition ArgTraits.h:59
virtual ~StringLikeTrait()
Definition ArgTraits.h:60
A string like argument value type is a value that can be set using operator=(string).
Definition ArgTraits.h:49
virtual ~StringLike()
Definition ArgTraits.h:50
A class can inherit from this object to make it have value like traits.
Definition ArgTraits.h:68
virtual ~ValueLikeTrait()
Definition ArgTraits.h:70
ValueLike ValueCategory
Definition ArgTraits.h:69
A value like argument value type is a value that can be set using operator>>.
Definition ArgTraits.h:39
ValueLike ValueCategory
Definition ArgTraits.h:40
virtual ~ValueLike()
Definition ArgTraits.h:41