Standard Conversions

The C++ language defines conversions between its fundamental types. It also defines conversions for pointer, reference, and pointer-to-member derived types. These conversions are called “standard conversions.” (For more information about types, standard types, and derived types, see Types in Chapter 2.)

This chapter discusses the following standard conversions:

• Integral promotions
• Integral conversions
• Floating conversions
• Floating and integral conversions
• Arithmetic conversions
• Pointer conversions
• Reference conversions
• Pointer-to-member conversions

Note   User-defined types can specify their own conversions. Conversion of user-defined types is covered in Constructors and Conversions in Chapter 11.

The following code causes conversions (in this example, integral promotions):

long  lnum1, lnum2;
int   inum;

// inum promoted to type long prior to assignment.
lnum1 = inum;

// inum promoted to type long prior to multiplication.
lnum2 = inum * lnum2;

Note   The result of a conversion is an l-value only if it produces a reference type. For example, a user-defined conversion declared as

operator int&()

returns a reference and is an l-value. However, a conversion declared as

operator int()

returns an object and is not an l-value.