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/*
* Copyright (c) 2017 TOYOTA MOTOR CORPORATION
*
* 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
*
* http://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 TMCAGLWM_RESULT_HPP
#define TMCAGLWM_RESULT_HPP
#include <experimental/optional>
#include <functional>
namespace wm
{
using std::experimental::nullopt;
using std::experimental::optional;
// We only ever return a string as an error - so just parametrize
// this over result type T
template <typename T>
struct result
{
char const *e;
optional<T> t;
bool is_ok() const { return this->t != nullopt; }
bool is_err() const { return this->e != nullptr; }
T unwrap()
{
if (this->e != nullptr)
{
throw std::logic_error(this->e);
}
return this->t.value();
}
operator T() { return this->unwrap(); }
char const *unwrap_err() { return this->e; }
optional<T> const &ok() const { return this->t; }
optional<char const *> err() const
{
return this->e ? optional<char const *>(this->e) : nullopt;
}
result<T> map_err(std::function<char const *(char const *)> f);
};
template <typename T>
struct result<T> Err(char const *e)
{
return result<T>{e, nullopt};
}
template <typename T>
struct result<T> Ok(T t)
{
return result<T>{nullptr, t};
}
template <typename T>
result<T> result<T>::map_err(std::function<char const *(char const *)> f)
{
if (this->is_err())
{
return Err<T>(f(this->e));
}
return *this;
}
} // namespace wm
#endif // TMCAGLWM_RESULT_HPP
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