Code
Casting in C++
Common standard C++ extensions are templates, run-time type indentification RTTI, namespaces and exceptions. We will focus on an another new extension of C++ : Casting in C++. New casting operator are introduced.
The C++ draft standard includes the following four casting operator: 
static_cast const_cast dynamic_cast reinterpret_cast
Casts are used to convert a type to an another type. Some conversions are performed automatically by the compiler. These conversions are called implicit casts. Conversions explicity specified by the programmer are called explicit casts.
Older technical casts are: Conversion class X to class Y, define constructor Y(const X & x); Conversion class X to class Y, define Y class with operator X() int i; double(i); or (double)i;
Now, we use four new C++ casting operators: static_cast, to convert one type to another type const_cast, to cast away the ``const-ness’’ or ``volatile-ness’’ of a type dynamic_cast, for safe navigation of an inheritance hierarchy reinterpret_cast, to perform type conversions on un-related types
The static_cast operator
usage: static_cast< T > (expression);
example:
int numberOfClasses = 12;
double rate = static_cast<double>(students)/numberOfClasses;
The const_cast operator
usage: const_cast< T > (expression);
example:
{
i++;
return i;
}
void display(const int &i)
{
int t;
t = increment(const_cast<int&>(i));
cout << t << endl;
}
The dynamic_cast operator
usage: dynamic_cast< T > (expression);
example: TO DO
The reinterpret_cast operator
usage: reinterpret_cast< T > (expression);
example: TO DO
Conclusion
C++ cast operators enable you to develop programs which are easier to maintain, understand, and perform some conversions safely. Before using casts ask yourself if a cast is really needed. It may be that you are using a class hierarchy in a way not originally intended or that you may be able to do the same thing with file functions.
Author : hackervalley@free.fr http://hackervalley.free.fr
Copyright (c) 2003 hackervalley Permission is granted to copy, distribute and/or modify this document under the terms of the GNU Free Documentation License, Version 1.2 or any later version published by the Free Software Foundation; with no Invariant Sections, no Front-Cover Texts, and no Back-Cover Texts. A copy of the license is included in the section entitled "GNU Free Documentation License".
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