Type-casting in C++

Question

I'm studying C++ by two months using the book : Programming principles and practice using C++, and now I wanted to clarify some doubts about my casting. When I am performing an implicit conversion, for example :

char c = 'a'; 
int b = c; 

Here the value of c is implicitly converted to int type without using any explicit operator. Is this considered casting ? or its considered casting just when I have to performe an explicit conversion like in :

int a = 10; 
int b = 5.5; 
double sum = double (a) / b; 

I know it may sound a stupid question but I just wanted to be sure about conversions.

Answer 1

As mentioned in other answers, casts are written explicitly. The standard refers to them as explicit type conversions; [expr.cast]/2:

An explicit type conversion can be expressed using functional notation (5.2.3), a type conversion operator (dynamic_cast, static_cast, reinterpret_cast, const_cast), or the cast notation.

There are three kinds of expressions that we call casts, mentioned in the above quote:

• (T)expr. In the standard this form is called the cast notation of explicit type conversion and is also commonly referred to as a C-style cast (as it is the syntax used in and inherited from C). (double) a is an example.

• T(expr). This is the functional notation (also called function-style cast). Often used for creating temporaries of class type, e.g. std::string("Hello World"). double(a) is also a function-style cast.

• And last but not least, the so-called type conversion operators static_cast<T>(expr), reinterpret_cast, const_cast and dynamic_cast. These are the most explicit notations and are individually more restricted.

The use of all these is covered in this Q/A.

Every other conversion performed is not called a cast.

Answer 2

"Casting" is only when you perform an explicit conversion.

That being said, you will find the term misused all across the internet and in various teams!