What's the best way to go about doing this? Here's what I've got so far
(defn line-segment [start end]
(let [x-direction (abs (- (first end) (first start)))
y-direction (abs (- (last end) (last start)))]
(cond
(= 0 x-direction) (something ...)
(= 0 y-direction) (something ...))))
Here's my end goal
user=> (line-segment [5 6] [5 8])
([5 6] [5 7] [5 8])
And yes, there are no diagonals, only x or y movement.
Thanks.
I think this is a pretty elegant solution:
(defn line-segment [start end]
(let [x1 (first start) x2 (first end)
y1 (last start) y2 (last end)
dx (if (> x1 x2) -1 1)
dy (if (> y1 y2) -1 1)]
(for [x (range x1 (+ dx x2) dx)
y (range y1 (+ dy y2) dy)]
[x y])))
REPL session:
user> (line-segment [5 6] [5 8])
([5 6] [5 7] [5 8])
user> (line-segment [5 8] [5 6])
([5 8] [5 7] [5 6])
user> (line-segment [-2 7] [1 7])
([-2 7] [-1 7] [0 7] [1 7])
user> (line-segment [1 7] [-2 7])
([1 7] [0 7] [-1 7] [-2 7])
This function returns a LazySeq even though your sample output was formatted as a vector. I figured this wasn't important.
Here's a simple solution that also allows diagonals:
(use 'clojure.contrib.math)
(defn line-segment [start end]
(let [x1 (first start) x2 (first end)
y1 (last start) y2 (last end)
xdiff (- x2 x1)
ydiff (- y2 y1)
maxdiff (max (abs xdiff) (abs ydiff))
dx (/ xdiff maxdiff)
dy (/ ydiff maxdiff)]
(for [i (range (inc maxdiff))]
[(round (+ x1 (* i dx))) (round (+ y1 (* i dy)))])))
As with dbryne's solution, this returns a lazy sequence of points rather than a vector: I think this is the most useful form assuming that you subsequently want to do something with each of the points on the line segment in turn.
