; All this negative-int is not *directly* possible in .rot
; sorry. -but what counts is this:
;  if you can't imagine it with positive ints;
; All this floating-point is not *directly* possible in .rot
;  if you can't imagine it with whole numbers;
;  you can't it!
; PUT IN ANOTHER WAY:
;  if you do it,
;   you can it.
;  if you take it,
;   you can it.
;  if you only request of it, (own it)
;   you cannot one single bit of it!

(DEFINE X 3)
(DEFINE (SQUARE X) (* X X))
(DEFINE SQUARE (LAMBDA (X) (* X X)))
; "black-box abstraction" 1A:(18m)
; What is a programming language?
; => What is Lisp? 1A:(28m)
(DEFINE (AVERAGE X Y)
  (/ (+ X Y) 2))
(DEFINE (MEAN-SQUARE X Y)
  (AVERAGE (SQUARE X)
           (SQUARE Y)))
; Case Analysis 1A:(51m)
(DEFINE (ABS X)
  (COND ((< X 0) (- X))
        ((= X 0) (0))
	((> X 0) X)))
; "blackbox" block-structure 1A:(1h 07m)
(DEFINE (SQRT X)
  (DEFINE (IMPROVE GUESS)
    (AVERAGE GUESS (/ X GUESS)))
  (DEFINE (GOOD-ENOUGH? GUESS)
    (< (ABS (- (SQUARE GUESS) X))
       .001))
  (DEFINE (TRY GUESS)
    (IF (GOOD-ENOUGH? GUESS)
        GUESS
        (TRY (IMPROVE GUESS))))
  (TRY 1))

; BREAK 1A:(27m40s) There are three meters for a programming language.
;  * What are the PRIMITIVE ELEMENTS contained therein?
;     (The so called primitives)
;  * What are the MEANS OF COMBINATION?
;     (The way to express relation between those primitives)
;  * What are the MEANS OF ABSTRACTION?
;     (The way to hide simplicity (to create complexity))

; SUMMARIZING 1A:(1h8m49s) the three meters for LISP.
; (END)