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

Function return values

A C++ function prototype must specify the return value type of the function (in C, if you leave off the return value type it defaults to int). The return type specification precedes the function name. To specify that no value is returned, use the void keyword. This will generate an error if you try to return a value from the function. Here are some complete function prototypes:

int f1(void); // Returns an int, takes no arguments
int f2(); // Like f1() in C++ but not in Standard C!
float f3(float, int, char, double); // Returns a float
void f4(void); // Takes no arguments, returns nothing

To return a value from a function, you use the return statement. return exits the function back to the point right after the function call. If return has an argument, that argument becomes the return value of the function. If a function says that it will return a particular type, then each return statement must return that type. You can have more than one return statement in a function definition:

//: C03:Return.cpp
// Use of "return"
#include <iostream>
using namespace std;

char cfunc(int i) {
  if(i == 0)
    return 'a';
  if(i == 1)
    return 'g';
  if(i == 5)
    return 'z';
  return 'c';

int main() {
  cout << "type an integer: ";
  int val;
  cin >> val;
  cout << cfunc(val) << endl;
} ///:~

In cfunc( ), the first if that evaluates to true exits the function via the return statement. Notice that a function declaration is not necessary because the function definition appears before it is used in main( ), so the compiler knows about it from that function definition.

Thinking in C++
Prev Contents / Index Next

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