#!/usr/local/bin/sbcl --script
(;; Learning to code Common Lisp
;; This lisp calculates the area of a circle
;; Courtesy of www.tutorialspoint.com/lisp/lisp_input_output.htm
;;
;; the function AreaOfCircle
;; calculates the area of a circle
;; when the radius is input from keyboard

(defun AreaOfCircle ())  ;; AreaOfCircle is defined as a blank function at this time
(terpri) ;; prints a newline
(princ "Enter Radius: ")  ;; format t,, prin1 and princ all prints to the screen
                          ;; princ tends to look better at it, though
(setq radius (read))      ;; setq sets a variable ( in C this would have to defined as an integer
                          ;; float, long float...etc.. at the top as Int long float (radius)
                          ;;
(setq area (* 3.1416 radius radius)) ;; declare another function called radius which equals
                                     ;; whatever our raidius is times pi (3.1416)  * radius to 
                                     ;; the second power to create the area itself
                                     ;;
(write area)                         ;; Now that we've done the math, we need to print it to the 
                                     ;; screen as the variable Area. That's what this command is doing
                                     ;; at this point.
                                     ;;
(AreaOfCircle)                       ;; Now we're giving program a routine to start with, which 
                                     ;; we've already created at the top, analogous to the C 
                                     ;; (int main ), however, we don't have to declare a main
                                     ;; on this program, just give it the routine name to start with.