C++ Increment and Decrement Operators
The increment operator ++ adds 1 to the operand, and the decrement operator -- subtracts 1 from the operand. Therefore:
x = x+1; 等同于 x++;
Similarly:
x = x-1; 等同于 x--;
Both the increment and decrement operators can be placed before (prefix) or after (suffix) the operand. For example:
x = x+1; 可以写成： ++x; // 前缀形式
Or:
x++; // 后缀形式
There is a slight difference between the prefix and suffix forms. If the prefix form is used, the increment or decrement is completed before the expression is evaluated; if the suffix form is used, the increment or decrement is completed after the expression is evaluated.
Example
Please look at the following example to understand the difference between the two:
Example
#include <iostream>
using namespace std;
int main()
{
int a = 21;
int c ;
// The value of a is not incremented before assignment
c = a++;
cout << "Line 1 - Value of a++ is :" << c << endl ;
// After evaluating the expression, the value of a is increased by 1
cout << "Line 2 - Value of a is :" << a << endl ;
// The value of a is incremented before assignment
c = ++a;
cout << "Line 3 - Value of ++a is :" << c << endl ;
return 0;
}
When the above code is compiled and executed, it produces the following results:
Line 1 - Value of a++ is :21 Line 2 - Value of a is :22 Line 3 - Value of ++a is :23other extensions