Make a Function

In LISP, we can make function that have procedure in it. With function, we can resolve complicated problems with just a command. To make a function, follow the instruction below:

1. Determine the name of the function and what parameter we need. 
2. Determine what problem we will solve. Make a plan how to resolve the problem.
3. Write the function in LISP. 
4. Format of the function is 

                  (defun function-name (parameter1 parameter2 parameter3 ...)

                           (process how to solve problem)

                  )

Some example:

1. This function will add a b. 

    (defun add (a b)

         (+ a b)

    )

2. This function will multiple a to b

    (defun multiple (a b)

          (* a b)

    )

In LISP, we just need to write the name of function.

1. (add 4 5) 

    ==> 9

2. (multiple 3 4)

    ==> 12

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