$\newcommand{\W}[1]{ \; #1 \; } \newcommand{\R}[1]{ {\rm #1} } \newcommand{\B}[1]{ {\bf #1} } \newcommand{\D}[2]{ \frac{\partial #1}{\partial #2} } \newcommand{\DD}[3]{ \frac{\partial^2 #1}{\partial #2 \partial #3} } \newcommand{\Dpow}[2]{ \frac{\partial^{#1}}{\partial {#2}^{#1}} } \newcommand{\dpow}[2]{ \frac{ {\rm d}^{#1}}{{\rm d}\, {#2}^{#1}} }$
 # include <cppad/cppad.hpp> bool UnaryPlus(void) { bool ok = true; using CppAD::AD; // domain space vector size_t n = 1; CPPAD_TESTVECTOR(AD<double>) x(n); x[0] = 3.; // declare independent variables and start tape recording CppAD::Independent(x); // range space vector size_t m = 1; CPPAD_TESTVECTOR(AD<double>) y(m); y[0] = + x[0]; // create f: x -> y and stop tape recording CppAD::ADFun<double> f(x, y); // check values ok &= ( y[0] == 3. ); // forward computation of partials w.r.t. x[0] CPPAD_TESTVECTOR(double) dx(n); CPPAD_TESTVECTOR(double) dy(m); size_t p = 1; dx[0] = 1.; dy = f.Forward(p, dx); ok &= ( dy[0] == 1. ); // dy[0] / dx[0] // reverse computation of dertivative of y[0] CPPAD_TESTVECTOR(double) w(m); CPPAD_TESTVECTOR(double) dw(n); w[0] = 1.; dw = f.Reverse(p, w); ok &= ( dw[0] == 1. ); // dy[0] / dx[0] // use a VecAD<Base>::reference object with unary plus CppAD::VecAD<double> v(1); AD<double> zero(0); v[zero] = x[0]; AD<double> result = + v[zero]; ok &= (result == y[0]); return ok; }