On: Not Lisp again (2009)

[jcelerier]

Here's the generic C++ version (https://gcc.godbolt.org/z/mMln6L):

    constexpr double delta = 1.0e-6;
    
    constexpr auto deriv = [] (auto f) { 
        return [=] (double x) { 
            return (f(x+delta) - f(x)) / delta; 
        };
    };

    constexpr auto f¨ = [] (auto f) { return deriv(deriv(f)); }; 

    double res = f¨([] (double x) { return x*x*x; })(2.0);