Parameter types

Quote:

Original post by nGamer If I have a function void some_function (std::vector ), Is there anyway that I can have the function allow vectors containing all objects deriving from A be passed into this function?

What do you mean by "allow"? The current function declaration does just that: The function takes a vector (or rather, copies the vector*) of pointer-to-A-like-objects.

Are you asking whether or not you can cast a std::vector to a std::vector?

*Did you mean to pass the vector in by reference?:

void some_function( std::vector<A*>& avec );

As it were, I have a function,

that checks the object's position and set the objects' position back to the visible playing field if it is off-screen. But you see, I have vectors containing types of Entity that I would like to pass in.

Are templates out of the question?

template <class T>void test_entities_outOfFrame (std::vector <T*> *e, int width, int height){  for (unsigned int index = 0; index < e->size ();)  {    if ((*e)[index]->get_positionX () < 0) (*e)[index]->set_positionX (width) ;    if ((*e)[index]->get_positionX () > width) (*e)[index]->set_positionX (0) ;    if ((*e)[index]->get_positionY () < 0) (*e)[index]->set_positionY (height) ;    if ((*e)[index]->get_positionY () > height) (*e)[index]->set_positionY (0) ;    ++ index ;  }}

Now vector of any pointer having those methods would go.

If I read you right, what you want is a template function:

If class Derived inherits from class Base, this does not imply that vector can be passed to std::vector, by value or pointer or reference.

You can however write template functions:

// Don't pass std::vector by pointer if you can avoid it!template<typename T>void test_entities_outOfFrame (std::vector <T *> &e, int width, int height){  for (unsigned int index = 0; index < e.size () ; ++ index)  {    // Moving common sub-expressions into a named variable    // Can make your code easier to read    T &instance = e[index];    if (instance.get_positionX () < 0) instance.set_positionX (width) ;    if (instance.get_positionX () > width) instance.set_positionX (0) ;    if (instance.get_positionY () < 0) instance.set_positionY (height) ;    if (instance.get_positionY () > height) instance.set_positionY (0) ;    // don't increment here if you can do it in the for() statement  }}

[edit: Shrinkage's suggestion is a good one: unless you want compile-time duck typing]

Quote:

Original post by _fastcall Quote: Original post by nGamer If I have a function void some_function (std::vector ), Is there anyway that I can have the function allow vectors containing all objects deriving from A be passed into this function? Are you asking whether or not you can cast a std::vector to a std::vector?

That is what I meant. I apologize; when I typed in the less than symbol preceded by the capital 'A', the asterisk, and then the greater than symbol, my text was underlined in the post. How do I fix that?

Hold on.

Are you talking about a vector, or about a vector which contains Derived*s?

These are different cases.

For the first, you will need a template. For the second, you just pass it in, and rely on polymorphism (virtual dispatch) on each pointed-to instance.

But if you're not using polymorphism, why are you storing pointers to instances instead of just storing instances?