Question

In C# 4.0, you can use the “dynamic” keyword as a placeholder for a type that is not known until runtime. There are certain corner cases where this is extremely useful behavior. Is it possible to emulate anything like this in C++, possibly using C++0x features or RTTI?

Answer 1

Not really. The closest you can get is a void *, but you still need to cast it to an appropriate type before you can use it.

Update:

Trying to build a duck-typed DSL that compiles to C++, basically.

You can go about this in at least two ways:

Union-based variant

struct MyType {
  enum { NUMBER, STRING /* etc */ } type;
  union {
    double number;
    string str;
  };
};

Polymorphic class heirarchy

class MyType {
public:
  /* define pure virtual operations common to all types */
};

class MyNumber : public MyType {
private:
  double number;
public:
  /* implement operations for this type */
};