Recursive Function

Definition....

• A recursive function is one that calls itself repetitively until a final call is made thet no longer requires a self-call.
• Functions that call themselves
• Can only solve a base case
• Divide a problem up into
• What it can do
• What it cannot do
• What it cannot do resembles original problem
• The function launches a new copy of itself (recursion step) to solve what it cannot do.
• Eventually base case gets solved
• Gets plugged in, works its way up and solves whole problem.

Recursion: Factorials of nonnegative numbers

• Example: factorials
• 5! = 5 * 4 * 3 * 2 * 1
• Notice that 
• 5! = 5 * 4!
• 4! = 4 * 3!......
• It can compute factorials recursively
• Solve base case ( 1! = 0! = 1) then plug in
• 2! = 2 * 1! = 2 * 1 = 2 ;
• 3! = 3 * 2! = 3 * 2 = 6 ;

Recursive Evaluation of 5!