While converting some 2D code to 3D, I noticed that there are a bunch of methods in Double2D that are not in Double3D. Namely: add, subtract, length, lengthSq, multiply, resize, normalize, dot, and negate. Interestingly, MutableDouble3D seemed to have all of these. I went ahead and implemented them. I also added a 2 parameter constructor which takes a double x and double y. Since there are other constructors that take things like Double2Ds, I figured this isn't too bad. (it also saved me from a lot of code changes). Thanks, -Ben Ben Axelrod Research Scientist iRobot Corporation 8 Crosby Drive, Mail Stop 8-1 Bedford, MA 01730 (781) 430-3315 (Tel) (781) 960-2628 (Fax) [log in to unmask]