Skip to main content

Pointers to Function

Function Pointers is a rather confusing yet powerful feature of C++ programming language. Even if you have programming for a while I bet you have seen nothing like it, simply because they aren't’t needed in everyday programming.

Their most common use is in writing compilers and interpreters.

The main theory behind function pointers is, just like the contents of a variable can be accessed by a pointer, much the same way functions can also be invoked (called) by referencing it by a pointer to that function.

Although variables and functions are two separate identities, both of these are stored at some memory address which can be pointed (and hence accessed) by a pointer.

Going in detail of the working of function pointers will only confuse you so we skip that for now and move on to a simple example program.

The function defined in the program is made as simple as possible to reduce confusions. Please note that the program only illustrates how function pointers are declared and used but program doesn't’t serve any practical purpose.

  // -- Function Pointers --
  // Example program to illustrate how
  // pointer to function are declared
  // and used
  #include<iostream.h>

  // function prototype
  void func (void);

  void main(void)
  {
   // note the declaration of
   // of the pointer.
   // pointer is declared with void data type
   // because function's return
   // type is void, the void in the
   // parenthesis is due to the function
   // taking no (void) argument
   void (*func_ptr) (void);

   // just as array name without indices
   // gives the address, same way
   // function name without parenthesis
   // gives the address of the function
   func_ptr=func;

   cout<<"Function accessed directly:\n";
   func();

   cout<<"Function accessed via pointer:\n";
   (*func_ptr)();
  }

  void func(void)
  {
   cout<<"Simplest of the simple function\n\n";
  }

Good-Bye!

Related Articles:

Popular posts from this blog

Fix For Toshiba Satellite "RTC Battery is Low" Error (with Pictures)

RTC Battery is Low Error on a Toshiba Satellite laptop "RTC Battery is Low..." An error message flashing while you try to boot your laptop is enough to panic many people. But worry not! "RTC Battery" stands for Real-Time Clock battery which almost all laptops and PCs have on their motherboard to power the clock and sometimes to also keep the CMOS settings from getting erased while the system is switched off.  It is not uncommon for these batteries to last for years before requiring a replacement as the clock consumes very less power. And contrary to what some people tell you - they are not rechargeable or getting charged while your computer or laptop is running. In this article, we'll learn everything about RTC batteries and how to fix the error on your Toshiba Satellite laptop. What is an RTC Battery? RTC or CMOS batteries are small coin-shaped lithium batteries with a 3-volts output. Most laptops use

The Best Way(s) to Comment out PHP/HTML Code

PHP supports various styles of comments. Please check the following example: <?php // Single line comment code (); # Single line Comment code2 (); /* Multi Line comment code(); The code inside doesn't run */ // /* This doesn NOT start a multi-line comment block /* Multi line comment block The following line still ends the multi-line comment block //*/ The " # " comment style, though, is rarely used. Do note, in the example, that anything (even a multi-block comment /* ) after a " // " or " # " is a comment, and /* */ around any single-line comment overrides it. This information will come in handy when we learn about some neat tricks next. Comment out PHP Code Blocks Check the following code <?php //* Toggle line if ( 1 ) {      // } else {      // } //*/ //* Toggle line if ( 2 ) {      // } else {      // } //*/ Now see how easy it is to toggle a part of PHP code by just removing or adding a single " / " from th

Introduction to Operator Overloading in C++

a1 = a2 + a3; The above operation is valid, as you know if a1, a2 and a3 are instances of in-built Data Types . But what if those are, say objects of a Class ; is the operation valid? Yes, it is, if you overload the ‘+’ Operator in the class, to which a1, a2 and a3 belong. Operator overloading is used to give special meaning to the commonly used operators (such as +, -, * etc.) with respect to a class. By overloading operators, we can control or define how an operator should operate on data with respect to a class. Operators are overloaded in C++ by creating operator functions either as a member or a s a Friend Function of a class. Since creating member operator functions are easier, we’ll be using that method in this article. As I said operator functions are declared using the following general form: ret-type operator#(arg-list); and then defining it as a normal member function. Here, ret-type is commonly the name of the class itself as the ope