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Lesson 13 The const_cast and reinterpret_cast operators
Objective Define general form/use of const_cast/reinterpret_cast operators.

const_cast and reinterpret_cast C++ Operators

Examine the areas of casts and Runtime Type Identification

These topics are essential for writing programs that ensure type safety.
You should already be familiar with the static_cast operator. There are several other casting operators specific to the C++ language which have not been discussed so far in the course:
  1. const_cast, which removes the const attribute from a class
  2. reinterpret_cast, which reinterprets bits
  3. dynamic_cast, is used with classes having virtual functions

We will look at const_cast and reinterpret_cast in this lesson and dynamic_cast in the next lesson.
Use of const_cast and reinterpret_cast is rather dangerous, however these operators are necessary to provide a complete alternative to the old C-style casts. Please note that older compilers may not support the use of reinterpret_cast.


The const_cast operator has the form:
const_cast< type-id >( expression )
The const_cast operator can be used to remove the const attribute from a class. A pointer to any object type can be explicitly converted to a type that is identical except for the const qualifier. The result of this conversion will refer to the original object.


The reinterpret_cast operator has the form:
The reinterpret_cast operator can be used for conversions such as char* to int*, or any_class* to a completely_different_class*. These conversions, however, are extremely unsafe.
The safest use for the result of a reinterpret_cast is to cast it back to its original type.