--- /dev/null
+;;; Gacela, a GNU Guile extension for fast games development
+;;; Copyright (C) 2009 by Javier Sancho Fernandez <jsf at jsancho dot org>
+;;;
+;;; This program is free software: you can redistribute it and/or modify
+;;; it under the terms of the GNU General Public License as published by
+;;; the Free Software Foundation, either version 3 of the License, or
+;;; (at your option) any later version.
+;;;
+;;; This program is distributed in the hope that it will be useful,
+;;; but WITHOUT ANY WARRANTY; without even the implied warranty of
+;;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+;;; GNU General Public License for more details.
+;;;
+;;; You should have received a copy of the GNU General Public License
+;;; along with this program. If not, see <http://www.gnu.org/licenses/>.
+
+
+(define-module (gacela math)
+ #:export (*pi*
+ degrees-to-radians
+ radians-to-degrees
+ distance-between-points
+ nearest-power-of-two))
+
+
+;;; Constants
+
+(define *pi* (* (asin 1) 2))
+
+
+;;; Geometry
+
+(define (degrees-to-radians angle)
+ (/ (* angle *pi*) 180))
+
+(define (radians-to-degrees angle)
+ (/ (* angle 180) *pi*))
+
+(define (distance-between-points p1 p2)
+ (define (add-power-of-two p1 p2)
+ (cond ((null? p1)
+ 0)
+ (else
+ (+ (expt (- (car p1) (car p2)) 2)
+ (add-power-of-two (cdr p1) (cdr p2))))))
+
+ (cond ((not (= (length p1) (length p2)))
+ #f)
+ (else
+ (sqrt (add-power-of-two p1 p2)))))
+
+
+;;; Functions
+
+(define (nearest-power-of-two n)
+ (define (power p n)
+ (cond ((> (* p 2) n) p)
+ (else (power (* p 2) n))))
+ (power 1 n))