Postfix Expressions
Postfix expressions consist of primary expressions or expressions in which postfix operators follow a primary expression. The postfix operators are listed in the following table.
Postfix Operators
Operator Name |
Operator Notation |
|---|---|
[ ] |
|
( ) |
|
type-name( ) |
|
. or –> |
|
++ |
|
–– |
The following syntax describes possible postfix expressions:
primary-expression
postfix-expression [ expression ]
postfix-expression ( expression-list<SUB>opt</SUB> )
simple-type-name ( expression-list<SUB>opt</SUB> )
postfix-expression . name
postfix-expression –> name
postfix-expression ++
postfix-expression ––
cast-keyword < typename > (expression )
typeid ( typename )
The postfix-expression above may be a primary expression or another postfix expression. See primary expressions. Postfix expressions group left to right, thus allowing the expressions to be chained together as follows:
func(1)->GetValue()++
In the above expression, func is a primary expression, func(1) is a function postfix expression, func(1)->GetData is a postfix expression specifying a member of the class, func(1)->GetData() is another function postfix expression, and the entire expression is a postfix expression incrementing the return value of GetData. The meaning of the expression as a whole is "call func passing 1 as an argument and get a pointer to a class as a return value. Then call GetValue() on that class, then increment the value returned.
The expressions listed above are assignment expressions, meaning that the result of these expressions must be an r-value.
The postfix expression form
simple-type-name ( expression-list )
indicates the invocation of the constructor. If the simple-type-name is a fundamental type, the expression list must be a single expression, and this expression indicates a cast of the expression's value to the fundamental type. This type of cast expression mimics a constructor. Because this form allows fundamental types and classes to be constructed using the same syntax, this form is especially useful when defining template classes.
The cast-keyword is one of dynamic_cast, static_cast or reinterpret_cast. More information may be found in dynamic_cast, static_cast and reinterpet_cast.
The typeid operator is considered a postfix expression. See typeid operator.