;;; =======================================================
;;;  CMPU-101, Spring 2013
;;;  Assignment 6 
;;; =======================================================

(display "\n         CS101 Assignment 6, Spring 2013")
(display "\n          Please type your name here\n\n")

;; IMPORTANT!  MAKE SURE YOUR LINES OF CODE DO NOT WRAP WHEN 
;; YOUR WINDOW IS ABOUT 80 COLUMNS ACROSS. 

(require 2htdp/image)
(require 2htdp/universe)


(display "\n\n-----------------------------------\n")
(display "Problem 1: Drawing a grid")
(display "  \n-----------------------------------\n")

;  This is a 3 part problem that will produce a square    
;  grid with dimensions 800 X 800, like that shown below.
;  
;  NOTE: The first 2 parts of this problem are like the
;  last problem on lab 8.

.


; 
;  A list of posn pairs is either
;  1. empty, or
;  2. it's a (cons posnpr lopp), where posnpr is a list containing 2 
;     posns and lopp is a list of posn pairs.
; 


(display "\n\n    -------------------------------------------------------\n")
(display "    Problem 1(a): Making endpoints of horizontal grid lines")
(display "\n    -------------------------------------------------------\n") 
; 
;  Write a function called make-hor-endpoints, that consumes 2 numbers, a
;  side-length and spacing, and creates a list of lists. The contract,
;  header, and purpose for this function are given below.
;  
;  Each inner list will contain 2 posns.  These posns represent the ends of 
;  a line that will cross the scene from left to right. 
;  
;  Suppose side-length is 800 and spacing is 20. The first inner list will 
;  contain posns (0,20) and (800,20), the second inner list will contain 
;  posns (0,40) and (800,40), the third inner list will contain (0,60) and
;  (800, 60) and so on.  It may help you to sketch the empty scene and 
;  the endpoints before writing the function. With the given values of 
;  side-length and spacing, the x coordinate in each posn pair will be 0 
;  and 800, and the y coordinate will be in increments of 20 pixels, from 
;  20 to 800.
;  

 
;;Contract: 
;;Header:   
;;Purpose:  

;;Pre-function tests to uncomment: 
;;(this is a test with a smaller side-length and spacing)  
;(check-expect (make-hor-endpoints 40 10)
;              (list (list (make-posn 0 10) (make-posn 40 10)) 
;                    (list (make-posn 0 20) (make-posn 40 20)) 
;                    (list (make-posn 0 30) (make-posn 40 30))))


;;Function definition:



;;Post-function printfs to uncomment: 
;(printf "(make-hor-endpoints 100 20) => ~a~%" (make-hor-endpoints 100 20))
;(printf "(make-hor-endpoints 20 10) => ~a~%" (make-hor-endpoints 20 10))

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(display "\n\n    -------------------------------------------------------\n")
(display "    Problem 1(b): Making endpoints of vertical grid lines")
(display "\n    -------------------------------------------------------\n")
;  
;  Write a function called make-vert-endpoints, that consumes 2 numbers, a
;  side-length and spacing, and creates a list of lists. The contract,
;  header, and purpose for this function are given below.
;  
;  Each inner list will contain 2 posns.  These posns represent the ends of 
;  a line that will cross the scene from top to bottom. 
;  
;  Suppose side-length is 800 and spacing is 20. The first inner list will 
;  contain posns (20,0) and (20,800), the second inner list will contain 
;  posns (40,0) and (40,800), the third inner list will contain (60,0) and
;  (60,800) and so on.  It may help you to sketch the empty scene and 
;  the endpoints before writing the function. The y coordinate in each posn 
;  pair will be 0 and 800, and the x coordinate will be in increments of 
;  20 pixels, from 20 to 800.
;  

 
;;Contract: 
;;Header:   
;;Purpose:  

;;Pre-function tests to uncomment: 
;(check-expect (make-vert-endpoints 40 10)
;              (list (list (make-posn 10 0) (make-posn 10 40)) 
;                    (list (make-posn 20 0) (make-posn 20 40)) 
;                    (list (make-posn 30 0) (make-posn 30 40))))

;;Function definition:



;;Post-function printfs to uncomment: 
;(printf "(make-vert-endpoints 100 20) => ~a~%" (make-vert-endpoints 100 20))
;(printf "(make-vert-endpoints 20 10) => ~a~%" (make-vert-endpoints 20 10))



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(display "\n\n    -------------------------------------------------------\n")
(display "    Problem 1(c): Drawing lines between posn pairs ")
(display "\n    -------------------------------------------------------\n")     

; 
;  Write a function called draw-lines that creates a scene that shows
;  the grid shown at the start of problem 2.
;  
;  You should use the built-in function scene+line as part of the 
;  draw-lines function (instead of place-image). The scene+line
;  function consumes 6 arguments: an image, the x and y coordinates of 
;  one posn, the x and y coordinates of another posn, and a color, and   
;  draws a line of the specified color between one posn and the other. 
;  
;  The draw-lines function should consume a list of posn pairs and
;  produce a scene with lines between each pair of posns in the list. 
;  
;  Since this function returns a scene, there is a constant defined
;  for the empty-scene below.
;  


;;Uncomment the following constants for use in your function.
;(define SIDE 800)                     ;; Dimensions of grid
;(define MT (empty-scene SIDE SIDE))   ;; Base case for scene
;(define CLR "black")                  ;; Line color

;;Contract: (draw-lines list-of-posn-pairs) -> scene (image)
;;Header:   (define draw-lines (lambda (lopp) ... )) 
;;Purpose:  Add lines with endpoints specified by each posn pair to scene

;;Pre-function tests: By visual inspection.

;;Function definition:



;;Post-function printfs: 
;(printf "(draw-lines (make-hor-endpoints 800 20)) => ~%")
;(draw-lines (make-hor-endpoints 800 20))

;(printf "(draw-lines (make-vert-endpoints 800 20)) => ~%")
;(draw-lines (make-vert-endpoints 800 20))

;(define ENDPTS (append (make-hor-endpoints 800 20)
;                     (make-vert-endpoints 800 20)))
;(printf "(draw-lines ENDPTS) => ~%")
;(draw-lines ENDPTS)

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(display "\n\n----------------------------------------\n")
(display "Problem 2: Moving a circle across a grid")
(display "  \n----------------------------------------\n")
; 
;  Write a simulation of a small red circle moving left to right
;  across a grid.
;  
;  Uncomment the constants defined below and use them in a big-bang  
;  simulation.
;  


;; CONSTANTS USED IN SIMULATION:
;(define RADIUS 10)                              
;(define DIAMETER (* RADIUS 2))
;(define MODE "solid")
;(define COLOR "red")
;(define SEGMENT (circle RADIUS MODE COLOR))  
;(define GRID 
;  (draw-lines 
;   (append (make-hor-endpoints SIDE DIAMETER)
;           (make-vert-endpoints SIDE DIAMETER))))


; 
;  For this simulation, the world state w-s will be the current  
;  x coordinate of a red circle on a grid. The big-bang function  
;  will have 2 clauses, the on-draw and on-tick clauses.
;  
;  For the on-draw clause, you should complete a function called      
;  draw-segment that consumes a positive natural number called
;  w-s. This function should place the SEGMENT image at (x,y) 
;  coordinate (w-s, DIAMETER) on top of the GRID scene created
;  above.
;  
;  For the on-tick clause, you should complete a function called
;  go-left that consumes a positive natural number called w-s and
;  increases w-s by DIAMETER each time it is called.
;  


;;Contract: (draw-segment number) -> scene (image)
;;Header:   (define draw-segment (lambda (w-s) ...))
;;Purpose:  Render result of placing SEGMENT at position (w-s,DIAMETER)
;;          on the background GRID.

;;Pre-function tests: By visual inspection.


;;Function definition:
;(define draw-segment
;  (lambda (w-s)

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;;Contract: (go-right number) -> number
;;Header:   (define go-right (lambda (w-s) ...))
;;Purpose:  Add DIAMETER to w-s.

;;Pre-function tests: 
;(check-expect (go-right 20) 40)
;(check-expect (go-right 40) 60)

;;Function definition:
;(define go-right
;  (lambda (w-s)

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;; Lastly, uncomment the following invocation of the big-bang
;; function.  When you press Run, you should see a red circle
;; moving from left to right across a grid.
;(big-bang DIAMETER
;          (on-draw draw-segment)
;          (on-tick go-right .25))  ;; The clock will tick every quarter sec.

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