1//===-- Holds an expected or unexpected value -------------------*- C++ -*-===//
2//
3// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
4// See https://llvm.org/LICENSE.txt for license information.
5// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
6//
7//===----------------------------------------------------------------------===//
8
9#ifndef LLVM_LIBC_SRC___SUPPORT_CPP_EXPECTED_H
10#define LLVM_LIBC_SRC___SUPPORT_CPP_EXPECTED_H
11
12namespace LIBC_NAMESPACE::cpp {
13
14// This is used to hold an unexpected value so that a different constructor is
15// selected.
16template <class T> class unexpected {
17 T value;
18
19public:
20 constexpr explicit unexpected(T value) : value(value) {}
21 constexpr T error() { return value; }
22};
23
24template <class T, class E> class expected {
25 union {
26 T exp;
27 E unexp;
28 };
29 bool is_expected;
30
31public:
32 constexpr expected(T exp) : exp(exp), is_expected(true) {}
33 constexpr expected(unexpected<E> unexp)
34 : unexp(unexp.error()), is_expected(false) {}
35
36 constexpr bool has_value() const { return is_expected; }
37
38 constexpr T &value() { return exp; }
39 constexpr E &error() { return unexp; }
40 constexpr const T &value() const { return exp; }
41 constexpr const E &error() const { return unexp; }
42
43 constexpr operator bool() const { return is_expected; }
44
45 constexpr T &operator*() { return exp; }
46 constexpr const T &operator*() const { return exp; }
47 constexpr T *operator->() { return &exp; }
48 constexpr const T *operator->() const { return &exp; }
49};
50
51} // namespace LIBC_NAMESPACE::cpp
52
53#endif // LLVM_LIBC_SRC___SUPPORT_CPP_EXPECTED_H
54

source code of libc/src/__support/CPP/expected.h