;;; guile-2d
;;; Copyright (C) 2013 David Thompson <dthompson2@worcester.edu>
;;;
;;; Guile-2d is free software: you can redistribute it and/or modify it
;;; under the terms of the GNU Lesser General Public License as
;;; published by the Free Software Foundation, either version 3 of the
;;; License, or (at your option) any later version.
;;;
;;; Guile-2d 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
;;; Lesser General Public License for more details.
;;;
;;; You should have received a copy of the GNU Lesser General Public
;;; License along with this program.  If not, see
;;; <http://www.gnu.org/licenses/>.

;;; Commentary:
;;
;; Miscellaneous math procedures. Currently just trigonometry.
;;
;;; Code:

(define-module (2d math)
  #:export (pi
            degrees->radians
            radians->degress
            sin-degrees
            cos-degrees
            tan-degrees
            atan-degrees))

;; Dave was editing this module on Pi Approximation Day.
;;
;;       3.141592653589793238462643383279
;;     5028841971693993751058209749445923
;;    07816406286208998628034825342117067
;;    9821    48086         5132
;;   823      06647        09384
;;  46        09550        58223
;;  17        25359        4081
;;            2848         1117
;;            4502         8410
;;            2701         9385
;;           21105        55964
;;           46229        48954
;;           9303         81964
;;           4288         10975
;;          66593         34461
;;         284756         48233
;;         78678          31652        71
;;        2019091         456485       66
;;       9234603           48610454326648
;;      2133936            0726024914127
;;      3724587             00660631558
;;      817488               152092096
;;
(define pi 3.141592654)

(define (degrees->radians angle)
  "Converts angle in degrees to radians."
  (* angle (/ pi 180)))

(define (radians->degrees angle)
  "Converts angle in radians to degrees."
  (* angle (/ 180 pi)))

(define (sin-degrees angle)
  "Computes the sin of the angle expressed in degrees."
  (sin (degrees->radians angle)))

(define (cos-degrees angle)
  "Computes the cosine of the angle expressed in degrees."
  (cos (degrees->radians angle)))

(define (tan-degrees angle)
  "Computes the tangent of the angle expressed in degrees."
  (tan (degrees->radians angle)))

(define (atan-degrees y x)
  "Computes the arctangent in degrees of the coordinates x and y."
  (radians->degrees (atan y x)))