Vector declaration "expected parameter declarator"

Question

I have a line of code inside a class's private member variables:

vector<double> dQdt(3)

When compiling in xcode, this gives an error "expected parameter declarator." I think I provided sufficient info. I don't see anything wrong with this declaration.

Answer 1

You have to initialize the variable in the constructor's initializer list:

class X 
{
    private:
     vector<double> dQdt;
    public:
     X() : dQdt(3) {}
};