1 #ifndef STAN_MATH_MIX_FUNCTOR_DERIVATIVE_HPP
2 #define STAN_MATH_MIX_FUNCTOR_DERIVATIVE_HPP
3 
4 #include <stan/math/fwd/core.hpp>
5 #include <stan/math/prim/fun/Eigen.hpp>
6 #include <stan/math/rev/core.hpp>
7 #include <vector>
8 
9 namespace stan {
10 namespace math {
11 
12 /**
13  * Return the derivative of the specified univariate function at
14  * the specified argument.
15  *
16  * @tparam T Argument type
17  * @tparam F Function type
18  * @param[in] f Function
19  * @param[in] x Argument
20  * @param[out] fx Value of function applied to argument
21  * @param[out] dfx_dx Value of derivative
22  */
23 template <typename T, typename F>
derivative(const F & f,const T & x,T & fx,T & dfx_dx)24 void derivative(const F& f, const T& x, T& fx, T& dfx_dx) {
25   fvar<T> x_fvar = fvar<T>(x, 1.0);
26   fvar<T> fx_fvar = f(x_fvar);
27   fx = fx_fvar.val_;
28   dfx_dx = fx_fvar.d_;
29 }
30 
31 }  // namespace math
32 }  // namespace stan
33 #endif
34