80         auto low = high;  in findY()  local
81         --low;  in findY()
86             return high->first == x ? high->second : low->second;  in findY()
88             return ((high->first - x) * low->second + (x - low->first) * high->second)  in findY()
89                     / (high->first - low->first);  in findY()
95             const S interval =  high->first - low->first;  in findY()
98             if (mMemo.count(low->first) != 0) {  in findY()
99                 const S t = (x - low->first) / interval;  in findY()
101                 const auto &memo = mMemo[low->first];  in findY()
102                 return low->second + std::get<0>(memo) * t  in findY()
108             if (low != this->begin()) {  in findY()
109                 low2 = low;  in findY()
133                 sec = (high->second - low->second) / interval;  in findY()
135                         ? (low->second - low2->second) / (low->first - low2->first)  in findY()
151                         ? (high2->second - low->second) / (high2->first - low->first)  in findY()
173             const S t = (x - low->first) / interval;  in findY()
179                 const T dy = high->second - low->second;  in findY()
180                 const S c0 = low->second;  in findY()
184                 mMemo[low->first] = std::make_tuple(c1, c2, c3);  in findY()
193                 return h00 * low->second + (h10 * m0 + h11 * m1) * interval + h01 * high->second;  in findY()