Re: Dynamic polymorphism vs. Static polymorphism

"Axter" <>
1 Jun 2006 02:49:08 -0700
Cy Edmunds wrote:

"Axter" <> wrote in message

Cy Edmunds wrote:

"Luke Meyers" <> wrote in message

Cy Edmunds wrote:

"Krivenok Dmitry" <> wrote in message
All elements of a container must be of the same type. If it is a
smart pointer to a common base class we have dynamic polymorphism.
polymorphism can be accomplished using a flag to determine the actual

struct clumsy
int flag;
union (...} other_stuff;

Uh, I'm pretty sure this is not what most people mean by "static
polymorphism." How did you come to associate the term with this ugly

The "static"/"dynamic" distinction wrt polymorphism, as with e.g.
typing, refers to compile-time vs. run-time. With static polymorphism,
the actual type of the object is known at compile-time. The usual
(only?) mechanism in C++ for this is templates.


The original poster asked about heterogeneous containers. How would you
that with templates?

Check out the following example code:

Each of the above files have different levels of complexity for
creating a heterogeneous container.
The basic idea is to create a wrapper class that acts like an interface
to the different types.
Although the types don't have to derive from the same object, they do
have to have a common method or common data to access.

David Maisonave

Author of Axter's policy based smart pointers
Top ten member of C++ Expert Exchange:

These are all based on dynamic polymorphism:
class Coins
    virtual int GetValue()=0;

Any smart pointer can function as a template based wrapper for a polymorphic

The interface is based on dynamic polymorphism, but the target type is
static polymorphism.
The target types (Penny, Dime, ....) are not derived from any class,
and Coins is just an interface to the static type.
This method mixes both dynamic polymorphism an static polymorphism to
get a heterogeneous container.

And, yes you could use a smart pointer to do this with an interface
class like Coins and the static holder class like TargetClassHolder.
std::vector<smart_ptr<Coins> > heterogeneousContainer;


That would work too.

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-- Deuteronomy 12:27