* Copyright (C) 2015 Ivan Cukic <ivan.cukic(at)kde.org>
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License version 2,
* or (at your option) any later version, as published by the Free
* Software Foundation
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details
*
* You should have received a copy of the GNU General Public
* License along with this program; if not, write to the
* Free Software Foundation, Inc.,
* 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
*/
#ifndef UTILS_LAZY_VAL_H
#define UTILS_LAZY_VAL_H
namespace kamd {
namespace utils {
template <typename F>
class lazy_val {
public:
lazy_val(F f)
: _f(std::forward<F>(f))
, valueRetrieved(false)
{
}
private:
F _f;
mutable decltype(_f()) value;
mutable bool valueRetrieved;
public:
operator decltype(_f()) () const
{
if (!valueRetrieved) {
valueRetrieved = true;
value = _f();
}
return value;
}
};
template <typename F>
inline lazy_val<F> make_lazy_val(F && f)
{
return lazy_val<F>(std::forward<F>(f));
}
}
}
#endif
