; WARNING TO ALL READERS OF ANY AGE:
; THIS WILL CATAPULT YOU INTO 1st GRADE.
; IT GOES ROUND AND ROUND ABOUT RECTANGLES
;  ALL DAY LONG. -A RECTANGLE PARODY!

; Getting PROCEDURAL
; using definitions from the last time.
; (define make-vector cons)
; (define xcor car)
; (define ycor cdr)

; (define make-seg cons)
; (define seg-start car)
; (define seg-end cdr)
(make-seg (make-vector 2 3)
          (make-vector 5 1))
; That's now just a PAIR of PAIRS
; Introducing CLOSURE 3A:(5m47s)
; and Lisp's LISTS. 3A:(7m55s)
(CONS 1
  (CONS 2
    (CONS 3
      (CONS 4 NIL))))
;meaning the same as
(LIST 1 2 3 4)

(DEFINE 1-TO-4 (LIST 1 2 3 4))
(CAR 1-TO-4) ;-> 1
(CAR (CDR 1-TO-4)) ;-> 2
(CAR (CDR (CDR 1-TO-4))) ;-> 3

; 3A:(16m51s) Writing a LIST-PROCEDURE.
(DEFINE (MAP P L)
  (IF (NULL? L)
      NIL
      (CONS (P (CAR L))
            (MAP P (CDR L)))))
; then using the MAP-primitive to define
; (define (scale-list s l)
;   (map (lambda (item) (*item s))
;        l))
; ==> ABSTRACTION in MIND.
; 3A:(23m8s) Another form of LIST-PROCEDURE.
;
; (define (for-each proc list)
;   (cond ((null? list) "done")
;          (else (proc (car list))
;                (for-each proc
;                          (cdr list)))))
;
; QUESTIONS 3A:(24m57s) BREAK 3A:(28m23s)
; Henderson Escher Example
;   summarizing the first two themes of the course.
;     * List-Structure
;     * Issues of Abstraction -> 1A:(18m)
;         and Representation (Interfacing) -> 1A:(23m12s)
;     * Capturing Commonality (Higher Order Procedures)
;   introducing the third theme:
;     * Metalinguistic Abstraction -> 1A:(24m41s)
;         -> building syntactically complete new languages to more
;            easily describe specific (complex) systems.
;
;   Recapitulation on the topic in lecture 1A:
;      What are the meters of a programming language?
;        Its PRIMITIVES
;    AND its MEANS OF COMBINATION
;    AND its MEANS OF ABSTRACTION
;
; 3A:(30m12s) Peter Henderson's Program
;   "I hope by the end of this morning, if you are not already,
;    you will be completely confused about what the difference
;    between procedures and data are."
;     --Hal
;
; 1 PRIMITIVE 3A:(31m50s)
;    PICTURE
; MEANS OF COMBINATION 3A:(33m17s)
;    DEFINE, ROTATE, FLIP, BESIDE, ABOVE
; The primitive PICTURE is CLOSED (=> CLOSURE-PROPERTY) under the
; MEANS OF COMBINATION.

; Lisp Implementation Details... 3A:(38m)

; BREAK 3A:(48m28s)
; Why is it nice to do this THIS way?
; more implementation... Because the implementation is not anymore
;   limited by the primitives but the imagination!
; 3A:(54m15s) get the CLOSURE-PROPERTY!

; MEANS OF ABSTRACTION 3A:(?m)
; kidding... ABSTRACTION comes with the MEANS OF COMBINATION and
; the ability to name this COMBINATION.
; To hide simplicity   AND   create complexity.


; implementation ...
; 3A:(1h7m5s) I am lost.
; 3A:(1h7m48s) Creating a Sequence of Layers of LANGUAGE.
; Language of SCHEMES of COMBINATION
;
; Creating Languages, not programs.
;
; ==> TALKING ABOUT CHANGE IN DIFFERENT WAYS
;   (procedures as data, data as procedures, procedures defining the change)
; BREAK 3A:(1h14m43s) (END)