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;;; 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 helper procedures.
;;
;;; Code:
(define-module (2d helpers)
#:use-module (srfi srfi-1)
#:use-module (rnrs arithmetic bitwise)
#:export (any-equal?
logand?
rgba->gl-color))
(define (any-equal? elem . args)
"Returns true if elem equals any of the arguments and returns false
otherwise."
(any (lambda (e) (equal? elem e)) args))
(define (logand? . args)
"Returns true if the result of a bitwise AND of the integer
arguments is non-zero and returns false otherwise."
(not (zero? (apply logand args))))
(define (rgba->gl-color color)
"Converts an integer color code into OpenGL compatible color
values. Returns a list of four floating point numbers in range [0,1]."
(define (component offset)
(let ((mask (bitwise-arithmetic-shift-left #xff offset)))
(/ (bitwise-arithmetic-shift-right (logand mask color) offset) 255.0)))
(list (component 24)
(component 16)
(component 8)
(component 0)))
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