[python][test] Check/explain new functions Python::make(Differentiable)Function()

dune/fufem/test/dunepythontest.cc

@@ -718,16 +718,13 @@ int main(int argc, char** argv)
     }
 
     std::cout << std::endl;
-    std::cout << "Example 16: Creating Dune-functions functions manually *************************" << std::endl;
+    std::cout << "Example 16: Creating Dune-functions functions **********************************" << std::endl;
     {
-        // Functions implementing the interface in dune-functions can also be created manually
-        //
-        // it is also possible to import dictionaries of callable
-        // python objects into a map of functions.
+        // Functions implementing the interface in dune-functions can also be created
+        // directly
 
         using Domain = Dune::FieldVector<double, 3>;
         using Range = Dune::FieldVector<double, 2>;
-        using DerivativeRange = Dune::Functions::DefaultDerivativeTraits<Range(Domain)>::Range;
 
         pyMain.import("math");
         pyMain.runStream()
@@ -738,16 +735,29 @@ int main(int argc, char** argv)
             << std::endl << "fdf = (f, df)"
             << std::endl;
 
-        auto pyF = Python::Callable(pyMain.get("f"));
-        auto pyDF = Python::Callable(pyMain.get("df"));
-
-        auto f = makeDifferentiableFunctionFromCallables(
-                Dune::Functions::SignatureTag<Range(Domain)>(),
-                [=](auto&& x) { return pyF(x).template toC<Range>();},
-                [=](auto&& x) { return pyDF(x).template toC<DerivativeRange>();});
+        // makeDifferentiableFunction automatically converts to Python::Callable
+        auto f = Python::makeDifferentiableFunction<Range(Domain)>(pyMain.get("f"), pyMain.get("df"));
 
         std::cout << "Result of calling a function FV<double,2>(FV<double,3>) : " << f({1, 2, 3}) << std::endl;
         std::cout << "Result of calling the derivative of a function FV<double,2>(FV<double,3>) : " << derivative(f)({1, 2, 3}) << std::endl;
+
+        // functions can also be cretaed from labda expressions
+        auto pyG = Python::evaluate("lambda x: math.sin(x)");
+        auto pyDG = Python::evaluate("lambda x: math.cos(x)");
+        auto pyDDG = Python::evaluate("lambda x: -math.sin(x)");
+        auto pyDDDG = Python::evaluate("lambda x: -math.cos(x)");
+
+        auto g = Python::makeDifferentiableFunction<double(double)>(pyG, pyDG, pyDDG, pyDDDG, pyG);
+
+        std::cout << "Result of calling a function double(double) : " << g(0) << std::endl;
+        std::cout << "Result of calling the derivative of a function double(double) : " << derivative(g)(0) << std::endl;
+        std::cout << "Result of calling the 2nd derivative of a function double(double) : " << derivative(derivative(g))(0) << std::endl;
+        std::cout << "Result of calling the 3rd derivative of a function double(double) : " << derivative(derivative(derivative(g)))(0) << std::endl;
+        std::cout << "Result of calling the 4rd derivative of a function double(double) : " << derivative(derivative(derivative(derivative(g))))(0) << std::endl;
+
+        // If you only need the function but no derivatives, you can also use makeFunction()
+        auto h = Python::makeFunction<double(double)>(Python::evaluate("lambda x: x*x"));
+        std::cout << "Result of calling a function double(double) : " << h(0.5) << std::endl;
     }
 
     // Before exiting you should stop the python interpreter.