\(\newcommand{\W}[1]{ \; #1 \; }\) \(\newcommand{\R}[1]{ {\rm #1} }\) \(\newcommand{\B}[1]{ {\bf #1} }\) \(\newcommand{\D}[2]{ \frac{\partial #1}{\partial #2} }\) \(\newcommand{\DD}[3]{ \frac{\partial^2 #1}{\partial #2 \partial #3} }\) \(\newcommand{\Dpow}[2]{ \frac{\partial^{#1}}{\partial {#2}^{#1}} }\) \(\newcommand{\dpow}[2]{ \frac{ {\rm d}^{#1}}{{\rm d}\, {#2}^{#1}} }\)

value.cpp

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Convert From AD to its Base Type: Example and Test

# include <cppad/cppad.hpp>

bool Value(void)
{   bool ok = true;
    using CppAD::AD;
    using CppAD::Value;

    // domain space vector
    size_t n = 2;
    CPPAD_TESTVECTOR(AD<double>) x(n);
    x[0] = 3.;
    x[1] = 4.;

    // check value before recording
    ok &= (Value(x[0]) == 3.);
    ok &= (Value(x[1]) == 4.);

    // 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[1];

    // cannot call Value(x[j]) or Value(y[0]) here (currently variables)
    AD<double> p = 5.;        // p is a parameter (does not depend on x)
    ok &= (Value(p) == 5.);

    // create f: x -> y and stop tape recording
    CppAD::ADFun<double> f(x, y);

    // can call Value(x[j]) or Value(y[0]) here (currently parameters)
    ok &= (Value(x[0]) ==  3.);
    ok &= (Value(x[1]) ==  4.);
    ok &= (Value(y[0]) == -4.);

    return ok;
}