C++でニュートン法を美しく書く その２（再帰処理で書く） - Qiita

#include <iostream> auto solve_by_newton_method = []( auto func , double x ,double error , double delta ) { double x1 = x; double x2 = x1 + delta; double y1 = func(x1); double y2 = func(x2); double diff_x = (y2 - y1) / (x2 - x1); double next_x = x1 - y1 / diff_x; if (fabs(y1 - 0) < error) { return x1; } double answer = solve_by_newton_method(func, next_x, error , delta); return answer; }; int main