Problem Set 5

Language: Intermediate Student
Due: 11:59 PM Wednesday, Feb. 8

1 Practice with map and filter

Use map, filter and local (you don't need lambda) to define the following functions.

; pts-north : posn list-of-posn -> list-of-posn

; returns the posns from lop that are north of p,

; that is, whose y-coordinate is greater than p's y-coordinate

(define (pts-north p lop) ---)

; build-straight-line : num list-of-number -> list-of-posn

; returns a list of posns where the x-coordinate is n and

; the y-coordinate is a number in lon

; e.g., (build-straight-line 2 (list 1 2 3))

; should be (list (make-posn 2 1) (make-posn 2 2) (make-posn 2 3))

(define (build-straight-line n lon) ---)