VMATH (Thinking out loud in Common Lisp)

;;; Some rough ideas about what the VMATH library might be
(in-package "VMATH")

;;; Scalar is the basic floating type.
(deftype scalar `single-float)

;;; This represents a packed (SIMD/Altivec) floating point vector of 4 components
(deftype vector4 `(simple-array scalar (4))

;;; Quaternions can be represented with the same structure of vector4
(deftype quat `vector4)

;;; XYZW Accessosrs
(defmacro x (v) (aref ,v 0))
(defmacro y (v) (aref ,v 1))
(defmacro z (v) (aref ,v 2))
(defmacro w (v) (aref ,v 3))

;;; Example
(defun v4add (va vb vr)
(declare (type vector4 va vb vr))
(setf (x vr) (+ (x va) (y va))
(y vr) (+ (y va) (y vb))
(z vr) (+ (z va) (z vb))
(w vr) (+ (w va) (z vb)))
vr)

;;; Which one sounds better:
;;;
;;; 1. V4+ ?
;;; 2. V4ADD ?
;;; 3. +V4 ?
;;; 4. ADDV4 ?
;;;
;;; My vote is for 2. More assembly like syntax.

;;; How to reduce the consing?
;;; Example:
;;; (sqrt some-value)
;;; That would cons, and more importantly is too generic
;;; (declare (type scalar some-value))
;;; (sqrt (the positive-scalar some-value))
;;; Would avoid consing on some of the Lisp Compilers