X-Git-Url: https://git.jsancho.org/?p=dungeon-master.git;a=blobdiff_plain;f=dungeon-master%2Fgeom%2Fpoint.scm;h=3f471eb9fa706efac47d2349b99e2b4ce1ad4bf9;hp=64faaac44a4c7b8e3272a463071418ce6bebea50;hb=d4dcc4ec9815f1574eb12b3ee20aa0362f77704b;hpb=09c4aef3b2dde4e8fdf0a4b673b36c1ddbc84b6e

diff --git a/dungeon-master/geom/point.scm b/dungeon-master/geom/point.scm
index 64faaac..3f471eb 100644
--- a/dungeon-master/geom/point.scm
+++ b/dungeon-master/geom/point.scm
@@ -4,7 +4,9 @@
             point?
             point-x
             point-y
-	    points-distance))
+	    points-distance
+            sum-points
+            scale-point))
 
 (define-record-type <point>
   (make-point x y)
@@ -16,3 +18,19 @@
   (abs
    (sqrt (+ (expt (- (point-x p1) (point-x p2)) 2)
             (expt (- (point-y p1) (point-y p2)) 2)))))
+
+(define (sum-points . points-to-sum)
+  (let loop ((points points-to-sum)
+             (x 0)
+             (y 0))
+    (cond ((null? points)
+           (make-point x y))
+          (else
+           (loop (cdr points)
+                 (+ x (point-x (car points)))
+                 (+ y (point-y (car points))))))))
+
+(define (scale-point point scale)
+  (make-point
+   (* (point-x point) scale)
+   (* (point-y point) scale)))