Result Cache<Result(Args...)>::operator()(Args... args) {
argument_tuple tup{args...};
auto map_iter = map.find(tup);
bool insert = map_iter == map.end();
log.push_back(nullptr);
ScopeFailure guard([&] { log.pop_back(); });
if (insert)
map_iter = map.insert({tup, {tuple_invoke(fun, tup), {}}}).first;
log.back() = &map_iter->first;
if (! insert)
log.erase(map_iter->second.log_iter);
map_iter->second.log_iter = std::prev(log.end());
if (insert && map.size() > cap) {
map.erase(*log.front());
log.pop_front();
}
return map_iter->second.result;
}
