diff options
| -rw-r--r-- | 2d/actions.scm | 40 |
1 files changed, 40 insertions, 0 deletions
diff --git a/2d/actions.scm b/2d/actions.scm new file mode 100644 index 0000000..50b3a39 --- /dev/null +++ b/2d/actions.scm @@ -0,0 +1,40 @@ +;;; 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: +;; +;; Actions are composable procedures that perform an operation over a +;; period of game time. +;; +;;; Code: + +(define-module (2d actions) + #:use-module (2d coroutine) + #:export (lerp)) + +(define (lerp proc start end duration) + "Linearly interpolate a number from start to end. Calls proc with the +interpolated value every frame." + (let ((delta (- end start))) + (define (lerp-iter time) + (if (< time duration) + (begin + (proc (+ start (* delta (/ time duration)))) + (wait) + (lerp-iter (1+ time))) + (proc end))) + (lerp-iter 0))) |