CS 2135 Homework 7: Streams and Script Position

Due: February 25 (Tuesday) at 11:59pm via turnin (assignment name hwk7).

Assignment Goals

Exercises: Streams

  1. Write a program make-square-stream that produces an infinite stream of squares (1, 4, 9, 16, ...). Do this without using the stream-cons and stream-rest definitions from class (and don't define similar helpers/macros for yourself). I want to make sure you understand how streams work and are built without relying on these helpers. Assume that all you have is the stream-struct: (define-struct stream (first make-rest)).

Exercises: Script Position

Convert each of the following programs such that all calls to scripts are in script-position.

  1. (define (fscript x) (+ 3 (* 2 x)))
(define (gscript y z) (+ (* y y) (* z z)))
(fscript (gscript (fscript 7) 8))

  2. (define (square-script x) (* x x))
(define (tri-height x) (sqrt (- (square-script x) (square-script (* .5 x)))))

(define (shape-area shape-type size)
  (cond [(symbol=? shape-type 'circle) (* pi (square-script size))]
        [(symbol=? shape-type 'square) (square-script size)]
        [(symbol=? shape-type 'equilat-tri) (* size (tri-height size))]))

  3. ;; assume that fscript could be rewritten as fscript/web, taking an action
;;    as a second argument 

(define (map fscript L)
  (cond [(empty? L) empty]
        [(cons? L) (cons (fscript (first L))
                         (map fscript (rest L)))]))

  4. (define (prompt-read promptstr)
  (begin
    (printf "~a: " promptstr)
    (read)))

(define (prompt-script plist)
  (cond [(empty? plist) empty]
	[(cons? plist)
	 (cons (prompt-read (first plist))
	       (prompt-script (rest plist)))]))

What to Turn In

Turn in a single file hwk7.ss (or hwk7.scm) containing all code and documentation for this assignment. Make sure that both students' names are in a comment at the top of the file.

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