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// Copyright 2017 Elias Kosunen
//
// 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.
//
// This file is a part of scnlib:
// https://github.com/eliaskosunen/scnlib
#ifndef SCN_UTIL_OPTIONAL_H
#define SCN_UTIL_OPTIONAL_H
#include "memory.h"
namespace scn {
SCN_BEGIN_NAMESPACE
struct nullopt_t {
};
namespace {
static constexpr auto& nullopt = detail::static_const<nullopt_t>::value;
}
/**
* A very lackluster optional implementation.
* Useful when scanning non-default-constructible types, especially with
* <tuple_return.h>:
*
* \code{.cpp}
* // implement scn::scanner for optional<mytype>
* optional<mytype> val;
* scn::scan(source, "{}", val);
*
* // with tuple_return:
* auto [result, val] = scn::scan_tuple<optional<mytype>>(source, "{}");
* \endcode
*/
template <typename T>
class optional {
public:
using value_type = T;
using storage_type = detail::erased_storage<T>;
optional() = default;
optional(nullopt_t) : m_storage{} {}
optional(value_type val) : m_storage(SCN_MOVE(val)) {}
optional& operator=(value_type val)
{
m_storage = storage_type(SCN_MOVE(val));
return *this;
}
SCN_NODISCARD constexpr bool has_value() const noexcept
{
return m_storage.operator bool();
}
constexpr explicit operator bool() const noexcept
{
return has_value();
}
SCN_CONSTEXPR14 T& get() noexcept
{
return m_storage.get();
}
SCN_CONSTEXPR14 const T& get() const noexcept
{
return m_storage.get();
}
SCN_CONSTEXPR14 T& operator*() noexcept
{
return get();
}
SCN_CONSTEXPR14 const T& operator*() const noexcept
{
return get();
}
SCN_CONSTEXPR14 T* operator->() noexcept
{
return m_storage.operator->();
}
SCN_CONSTEXPR14 const T* operator->() const noexcept
{
return m_storage.operator->();
}
private:
storage_type m_storage;
};
SCN_END_NAMESPACE
} // namespace scn
#endif
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