--- xast.c.orig	Wed Apr 19 17:39:04 2017
+++ xast.c	Wed Apr 19 17:40:03 2017
@@ -282,6 +282,7 @@ blastpair(i, j)		/* Generate random velocity vector v.
 #define rotinert(i)	(double) (obj[i].mass*shapesize[obj[i].shape]*shapesize[obj[i].shape])
 
 /* cause two objects to collide elastically	*/
+void
 bounce(i, j)
 int	i,j;
 {
