There are several problems with old type C casts. First, the syntax is the same for every casting operation. This means it is impossible to tell the purpose of the cast
Another problem is finding all the casts in a large file. Parentheses with an identifier between them are used throughout C and C++ programs. There is no easy way to search a source file and get a list of all the casts being performed.
Another problem with the old C cast is that it allows you to cast practically any type to any other type. This allows you to circumvent the safety of type checking. Using the new C++ style casting operators will make your programs more readable (easier to maintain) and less error-prone.
The casts consist of:
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static_cast |
convert one type to another type |
|
const_cast |
to remove the constant nature of a type |
|
dynamic_cast |
for navigation of an inheritance hierarchy |
|
reinterpret_cast |
perform type conversions on un-related types |
All of the casting operators have the same syntax and are used in a manner similar to what we will see later in the course when we cover templates.
static_cast is the most general and is intended as a replacement for most C-style casts. const_cast is used to remove the const from a type. The other two forms are for specific circumstances that should be researched when or if they are encountered.An example of a static_cast is one that can perform arithmetic conversions, such as from int to double. To avoid integer truncation in the following computation:
int num = 7;
int denom = 3;
double fraction = 7/3;
Becomes:double rate = static_cast<double>(num)/denom;
Bottom line... While you need a basic understanding of these casts, you can get through this course without mastering all aspects of all of these types of casts.
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