Prefix Increment and Decrement Operators:  ++, --

  • 项目

unary-expression :

++ unary-expression
--unary-expression

The unary operators (++ and --) are called “prefix” increment or decrement operators when the increment or decrement operators appear before the operand. Postfix increment and decrement has higher precedence than prefix increment and decrement operators. The operand must have integral, floating, or pointer type and must be a modifiable l-value expression (an expression without the const attribute). The result is not an l-value.

When the operator appears before its operand, the operand is incremented or decremented and its new value is the result of the expression.

For more information, see Postfix Increment and Decrement Operators.

Example

In the following example, first the variable nNum2 is incremented. Then the sum of nNum1 and nNum2 is placed into nTotal.

// Example of the prefix increment operator
int nNum1=1, nNum2=2, nTotal;

nTotal = (nNum1) + (++nNum2);   // nTotal now is 4