Recursion

Recursion

Definition: 

    A function containing either a call statement to itself or a call statement to another function that may result in a call statement back to the original function , this type of function is known as recursive function(the procedure is called recursion).

 

Well defined recursive function:

In order that a program should not indefinitely a recursive function must have the following properties…

1. There must be certain criteria, known as base criteria. For which the function doesn’t call itself.
2. Each time the function does call itself, either directly or indirectly and it must be closer to base criteria.

A recursive function with this two properties is said to be well defined.

Principles of recursive function:

For implementing and designing the good recursive program we must make certain assumption like

1. Base case: it is the terminating condition for the problem while designing any recursive algorithm, we must choose a proper terminating condition for the problem.
2. If condition: It provides the terminating criteria.
3. Every time a new recursive call is made, a new memory space is allocated to each automatic variable used by the recursive routine.
4. Each time recursive call is there, the duplicates values of the local variables of the recursive call are pushed into the stack, within respective call & all these values are available to the respective function, call when it is popped of from the stack. 
5. Recursive case: generally, else part of the recursive definitions calls the functions recursively.

Disadvantages of recursion:

• It consumes more storage space because the recursive calls along with the automatic variables are stored on the stack.

• The computer may run out of memory if the recursive calls are not checked.
• It is not more efficient I terms of speed & execution time.
• If proper precautions are not taken, recursive may result in non terminating functions.
• In recursion we can’t implement the concept of looping.