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
|
// Copyright 2019 Google LLC
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// https://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
#ifndef dap_optional_h
#define dap_optional_h
#include <assert.h>
#include <type_traits>
#include <utility> // std::move, std::forward
namespace dap {
// optional holds an 'optional' contained value.
// This is similar to C++17's std::optional.
template <typename T>
class optional {
template <typename U>
using IsConvertibleToT =
typename std::enable_if<std::is_convertible<U, T>::value>::type;
public:
using value_type = T;
// constructors
inline optional() = default;
inline optional(const optional& other);
inline optional(optional&& other);
template <typename U>
inline optional(const optional<U>& other);
template <typename U>
inline optional(optional<U>&& other);
template <typename U = value_type, typename = IsConvertibleToT<U>>
inline optional(U&& value);
// value() returns the contained value.
// If the optional does not contain a value, then value() will assert.
inline T& value();
inline const T& value() const;
// value() returns the contained value, or defaultValue if the optional does
// not contain a value.
inline const T& value(const T& defaultValue) const;
// operator bool() returns true if the optional contains a value.
inline explicit operator bool() const noexcept;
// has_value() returns true if the optional contains a value.
inline bool has_value() const;
// assignment
inline optional& operator=(const optional& other);
inline optional& operator=(optional&& other) noexcept;
template <typename U = T, typename = IsConvertibleToT<U>>
inline optional& operator=(U&& value);
template <typename U>
inline optional& operator=(const optional<U>& other);
template <typename U>
inline optional& operator=(optional<U>&& other);
// value access
inline const T* operator->() const;
inline T* operator->();
inline const T& operator*() const;
inline T& operator*();
private:
T val{};
bool set = false;
};
template <typename T>
optional<T>::optional(const optional& other) : val(other.val), set(other.set) {}
template <typename T>
optional<T>::optional(optional&& other)
: val(std::move(other.val)), set(other.set) {}
template <typename T>
template <typename U>
optional<T>::optional(const optional<U>& other) : set(other.has_value()) {
if (set) {
val = static_cast<T>(other.value());
}
}
template <typename T>
template <typename U>
optional<T>::optional(optional<U>&& other) : set(other.has_value()) {
if (set) {
val = static_cast<T>(std::move(other.value()));
}
}
template <typename T>
template <typename U /*= T*/, typename>
optional<T>::optional(U&& value) : val(std::forward<U>(value)), set(true) {}
template <typename T>
T& optional<T>::value() {
assert(set);
return val;
}
template <typename T>
const T& optional<T>::value() const {
assert(set);
return val;
}
template <typename T>
const T& optional<T>::value(const T& defaultValue) const {
if (!has_value()) {
return defaultValue;
}
return val;
}
template <typename T>
optional<T>::operator bool() const noexcept {
return set;
}
template <typename T>
bool optional<T>::has_value() const {
return set;
}
template <typename T>
optional<T>& optional<T>::operator=(const optional& other) {
val = other.val;
set = other.set;
return *this;
}
template <typename T>
optional<T>& optional<T>::operator=(optional&& other) noexcept {
val = std::move(other.val);
set = other.set;
return *this;
}
template <typename T>
template <typename U /* = T */, typename>
optional<T>& optional<T>::operator=(U&& value) {
val = std::forward<U>(value);
set = true;
return *this;
}
template <typename T>
template <typename U>
optional<T>& optional<T>::operator=(const optional<U>& other) {
val = other.val;
set = other.set;
return *this;
}
template <typename T>
template <typename U>
optional<T>& optional<T>::operator=(optional<U>&& other) {
val = std::move(other.val);
set = other.set;
return *this;
}
template <typename T>
const T* optional<T>::operator->() const {
assert(set);
return &val;
}
template <typename T>
T* optional<T>::operator->() {
assert(set);
return &val;
}
template <typename T>
const T& optional<T>::operator*() const {
assert(set);
return val;
}
template <typename T>
T& optional<T>::operator*() {
assert(set);
return val;
}
template <class T, class U>
inline bool operator==(const optional<T>& lhs, const optional<U>& rhs) {
if (!lhs.has_value() && !rhs.has_value()) {
return true;
}
if (!lhs.has_value() || !rhs.has_value()) {
return false;
}
return lhs.value() == rhs.value();
}
template <class T, class U>
inline bool operator!=(const optional<T>& lhs, const optional<U>& rhs) {
return !(lhs == rhs);
}
template <class T, class U>
inline bool operator<(const optional<T>& lhs, const optional<U>& rhs) {
if (!rhs.has_value()) {
return false;
}
if (!lhs.has_value()) {
return true;
}
return lhs.value() < rhs.value();
}
template <class T, class U>
inline bool operator<=(const optional<T>& lhs, const optional<U>& rhs) {
if (!lhs.has_value()) {
return true;
}
if (!rhs.has_value()) {
return false;
}
return lhs.value() <= rhs.value();
}
template <class T, class U>
inline bool operator>(const optional<T>& lhs, const optional<U>& rhs) {
if (!lhs.has_value()) {
return false;
}
if (!rhs.has_value()) {
return true;
}
return lhs.value() > rhs.value();
}
template <class T, class U>
inline bool operator>=(const optional<T>& lhs, const optional<U>& rhs) {
if (!rhs.has_value()) {
return true;
}
if (!lhs.has_value()) {
return false;
}
return lhs.value() >= rhs.value();
}
} // namespace dap
#endif // dap_optional_h
|
