Examples of function declarations

The following code fragments show several function declarations (or prototypes). The first declares a function f that takes two integer arguments and has a return type of void:

void f(int, int);

This fragment declares a pointer p1 to a function that takes a pointer to a constant character and returns an integer:

int (*p1) (const char*);

The following code fragment declares a function f1 that takes an integer argument, and returns a pointer to a function that takes an integer argument and returns an integer:

int (*f1(int)) (int);

Alternatively, a typedef can be used for the complicated return type of function f1:

typedef int f1_return_type(int);
f1_return_type* f1(int);

The following declaration is of an external function f2 that takes a constant integer as its first argument, can have a variable number and variable types of other arguments, and returns type int.

int extern f2(const int, ...);  /*  C version  */

int extern f2(const int ...);  //  C++ version

Function f6 is a const class member function of class X, takes no arguments, and has a return type of int:

class X
{
public:
   int f6() const;
};

Function f4 takes no arguments, has return type void, and can throw class objects of types X and Y.

class X;
class Y;

// ...

void f4() throw(X,Y);