Re: Declaring a static const member of a class.

Luca Cerone wrote:


Meyer's singleton may fit your description better (to create x when you first
create QuadFun -- that is, not to initialize it at all if you do not create
them). For example:

class QuadFun{
   public:
     QuadFun(double a, double b) ; // a and b will be used to initialize
     // the private vector y to evaluate the values (x-a)*(x-b)
     // x has to be a vector that is shared among all the object of the class.
   private:
     static const std::vector<double> &GetX() {
    static std::auto_ptr<const std::vector<double> >
        x(InitializeXFromConfigFile());
    return *x;
     }
     static std::vector<double> * InitializeXFromConfigFile(); // not shown
// this will be a vector of uniformly
            //spaced numbers from 0 to 1. The number of points is determined
            //by reading a configuration file. in this example I set the
            //number manually in the main function.
     std::vector<double> y;
}

QuadFun::QuadFun(double a, double b): y() {
    const std::vector<double> &x = GetX();
    unsigned n = x.size();
    y.reserve(n);
    for (unsigned i = 0; i < n; ++i)
        y[i] = (x[i] - a) * (x[i] - b);
}

Disclaimers: I did not try to complile the above and Meyer's singletons "in
pure" are not "thread-safe".

HTH
-Pavel