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// Copyright Matthew Pulver 2018 - 2019.
// Distributed under the Boost Software License, Version 1.0.
// (See accompanying file LICENSE_1_0.txt or copy at
// https://www.boost.org/LICENSE_1_0.txt)
#include <boost/math/differentiation/autodiff.hpp>
#include <iostream>
template <typename T>
T fourth_power(T const& x) {
T x4 = x * x; // retval in operator*() uses x4's memory via NRVO.
x4 *= x4; // No copies of x4 are made within operator*=() even when squaring.
return x4; // x4 uses y's memory in main() via NRVO.
}
int main() {
using namespace boost::math::differentiation;
constexpr unsigned Order = 5; // Highest order derivative to be calculated.
auto const x = make_fvar<double, Order>(2.0); // Find derivatives at x=2.
auto const y = fourth_power(x);
for (unsigned i = 0; i <= Order; ++i)
std::cout << "y.derivative(" << i << ") = " << y.derivative(i) << std::endl;
return 0;
}
/*
Output:
y.derivative(0) = 16
y.derivative(1) = 32
y.derivative(2) = 48
y.derivative(3) = 48
y.derivative(4) = 24
y.derivative(5) = 0
**/
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