Distances

Finding Distances I

The most straightforward way to figure out the distance to the closest warehouse is two steps:

1. (find-distances) Given a list of warehouse locations, make a list of distances from your location to all of them.
2. (minimum) Given a list of distances, find the smallest one.

Start out by writing some test cases, going from one warehouse to many.

;; find-distances: posn(current) list-of-posn(warehouses) -> list-of-numbers
(define (find-distances current warehouses)
  (list 0))
(check-expect (find-distances (make-posn 5 3) 
                              (list (make-posn 0 2) (make-posn 1 10)))
              (list 6 11))

Finding Distances II

NOTE: While this approach works, students may find it easier just to take the list of points from the grid making functions and directly plot their distances to depots.

Combine the results of the previous two sections to create a list of (list posn number) where the list records the distance from the posn to the nearest warehouse.

;; find-distances-2: list-of-posn(warehouses) list-of-posn(points) -> list of (posn, number)
(define (find-distances-2 warehouses points)
   (list (list (make-posn -1 -2) 5)))
(check-expect (find-distances-2 (list (posn 4 1) (posn 7 8))
                                (list (make-posn 0 0) (make-posn 2 7)))
              (list (5 6)))