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@(@\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}} }@)@ This is cppad-20221105 documentation. Here is a link to its current documentation .
Switching Between Variables and Dynamic Parameters: Example and Test

Function
For each ADFun object there is a corresponding function @(@ f(x, p) @)@ where x is the vector of independent variables and p is the vector of independent dynamic parameters.

Convert a Function to a Graph
The to_graph routine can be used to convert a ADFun to a graph representation; see cpp_ad_graph .

Convert a Graph to a Function
The from_graph routine can be used to convert a graph back to a function. During this conversion, it is possible to change dynamic parameters to variables and variables to dynamic parameters; see dyn2var and var2dyn in the from_graph documentation. Note that many such conversions can be done using the same cpp_ad_graph object.

Source Code 

# include <cppad/cppad.hpp>

bool switch_var_dyn(void)
{   bool ok = true;
    using std::string;
    //
    // f(x_0, x_1, x_2) = y_0 = x_2 * ( x_0 + x_1 );
    CPPAD_TESTVECTOR( CppAD::AD<double> ) ax(3), ay(1);
    for(size_t j = 0; j < 3; ++j)
        ax[j] = CppAD::AD<double>(j);
    Independent(ax);
    ay[0] = ax[2] * ( ax[0] + ax[1] );
    CppAD::ADFun<double> f(ax, ay);
    ok &= f.Domain() == 3;
    ok &= f.Range() == 1;
    ok &= f.size_dyn_ind() == 0;
    //
    // set independent variables and parameters
    CPPAD_TESTVECTOR(double) p(0), x(3);
    x[0] = 2.0;
    x[1] = 3.0;
    x[2] = 4.0;
    //
    // compute y = f(x)
    f.new_dynamic(p);
    CPPAD_TESTVECTOR(double) y = f.Forward(0, x);
    //
    // check result
    ok &= y[0] == x[2] * ( x[0] + x[1] );
    // -----------------------------------------------------------------------
    //
    // C++ graph object
    CppAD::cpp_graph graph_obj;
    f.to_graph(graph_obj);
    //
    // change x[0]->p[0], x[1]->p[1], x[2]->x[0]
    CppAD::vector<bool> dyn2var(0), var2dyn(3);
    var2dyn[0] = true;
    var2dyn[1] = true;
    var2dyn[2] = false;
    f.from_graph(graph_obj, dyn2var, var2dyn);
    p.resize(2);
    x.resize(1);
    //
    ok &= f.Domain() == 1;
    ok &= f.Range() == 1;
    ok &= f.size_dyn_ind() == 2;
    //
    // set independent variables and parameters
    p[0] = 1.0;
    p[1] = 2.0;
    x[0] = 3.0;
    //
    // compute y = f(x, p)
    f.new_dynamic(p);
    y = f.Forward(0, x);
    //
    // check result
    ok &= y[0] == x[0] * ( p[0] + p[1] );
    //
    return ok;
}
Input File: example/graph/switch_var_dyn.cpp