lst-0063-book.cpp
// https://godbolt.org/z/3MGbYn4d5
#include <iostream>
#include <chrono>
long fib(long n) { return n<2L ? 1L : fib(n-1L)+fib(n-2L); }
int main() {
using namespace std::chrono;
auto t0 = steady_clock::now(); // On your marks, get set …
auto res = fib(17); // … go!
auto t1 = steady_clock::now(); // Stop!
std::cout << "Result: " << res << "\n"; // Output: Result: 2584
std::cout << "Time: " << nanoseconds{t1-t0}.count() << "ns\n";
// Output: Time: 50727ns (e.g.)
}