Follow Techotopia on Twitter

On-line Guides
All Guides
eBook Store
iOS / Android
Linux for Beginners
Office Productivity
Linux Installation
Linux Security
Linux Utilities
Linux Virtualization
Linux Kernel
System/Network Admin
Scripting Languages
Development Tools
Web Development
GUI Toolkits/Desktop
Mail Systems
Eclipse Documentation

How To Guides
General System Admin
Linux Security
Linux Filesystems
Web Servers
Graphics & Desktop
PC Hardware
Problem Solutions
Privacy Policy




Thinking in C++
Prev Contents / Index Next

Auto increment and decrement

C, and therefore C++, is full of shortcuts. Shortcuts can make code much easier to type, and sometimes much harder to read. Perhaps the C language designers thought it would be easier to understand a tricky piece of code if your eyes didn’t have to scan as large an area of print.

One of the nicer shortcuts is the auto-increment and auto-decrement operators. You often use these to change loop variables, which control the number of times a loop executes.

The auto-decrement operator is ‘--’ and means “decrease by one unit.” The auto-increment operator is ‘++’ and means “increase by one unit.” If A is an int, for example, the expression ++A is equivalent to (A = A + 1). Auto-increment and auto-decrement operators produce the value of the variable as a result. If the operator appears before the variable, (i.e., ++A), the operation is first performed and the resulting value is produced. If the operator appears after the variable (i.e. A++), the current value is produced, and then the operation is performed. For example:

//: C03:AutoIncrement.cpp
// Shows use of auto-increment
// and auto-decrement operators.
#include <iostream>
using namespace std;

int main() {
  int i = 0;
  int j = 0;
  cout << ++i << endl; // Pre-increment
  cout << j++ << endl; // Post-increment
  cout << --i << endl; // Pre-decrement
  cout << j-- << endl; // Post decrement
} ///:~

If you’ve been wondering about the name “C++,” now you understand. It implies “one step beyond C.”

Thinking in C++
Prev Contents / Index Next

   Reproduced courtesy of Bruce Eckel, MindView, Inc. Design by Interspire