#### Oblivious

##### Is Kredit to Team!!

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- Joined
- Apr 30, 2008

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Just starting to learn this wonderful language, and was wondering if there was anyone else here who was experienced in this language to help me evaluate my style. I was learning C before this, so this might affect how I think about the problem.

Oh, it's working correctly (I think) at the very least for 3-dimensional vectors. I can't seem to find online calculators that evaluate higher dimensions then that.

(Is there anyone who knows the proper way to evaluate 7-dimensional vectors? Is it the same as 3-dimensional?)

The code below generalizes the following formula:

c = a Χ b

c0 = a1·b2 - a2·b1

c1 = -(b2·a0 - b0·a2)

c2 = a0·b1 - a1·b0

(I know its weird to have 0 value subscripts in math, but it matches array indexing, so it is clearer.)

Code:

```
[SIZE=2](defun cross-product (a b)
(let ((sub-1 1)) ;Subscripts refer to starting positions
(let ((sub-2 2)) ;These starting values correspond to first c0 value
(let ((result-vector(make-array (length a))))
(dotimes (i (length result-vector))
(setf (svref result-vector i) (- (* (svref a sub-1) (svref b sub-2))
(* (svref a sub-2) (svref b sub-1))
)) ;Main computation
(setf sub-1(move sub-1 (length a)))
(setf sub-2(move sub-2 (length a))))result-vector))))
(defun move (sub size) ;Subscript increment and reset
(if (= sub (1- size)) 0 (1+ sub)))
(setf *A* #(1 2 3))[/SIZE] [SIZE=2]
(setf *B* #(6 7 8))
(print(cross-product *A* *B*))[/SIZE]
```