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;;; Chickadee Game Toolkit
;;; Copyright © 2017 David Thompson <davet@gnu.org>
;;;
;;; Chickadee 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.
;;;
;;; Chickadee 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 (chickadee math easings)
#:use-module (chickadee math)
#:export (linear
smoothstep
ease-in-quad
ease-out-quad
ease-in-out-quad
ease-in-cubic
ease-out-cubic
ease-in-out-cubic
ease-in-quart
ease-out-quart
ease-in-out-quart
ease-in-quint
ease-out-quint
ease-in-out-quint
ease-in-sine
ease-out-sine
ease-in-out-sine))
(define-inlinable (linear t)
t)
(define-inlinable (smoothstep t)
(* t t (- 3 (* 2 t))))
(define-inlinable (ease-in-quad t)
(* t t))
(define-inlinable (ease-out-quad t)
(* t (- 2.0 t)))
(define-inlinable (ease-in-out-quad t)
(if (< t 0.5)
(* 2.0 t t)
(- (* (- 4 (* 2.0 t)) t) 1.0)))
(define-inlinable (ease-in-cubic t)
(* t t t))
(define-inlinable (ease-out-cubic t)
(let ((t* (- t 1.0)))
(+ 1.0 (* t* t* t*))))
(define-inlinable (ease-in-out t)
(if (< t 0.5)
(* 4.0 t t t)
(+ 1.0
(* (- t 1.0)
(* 2 (- t 2.0))
(* 2 (- t 2.0))))))
(define-inlinable (ease-in-quart t)
(* t t t t))
(define-inlinable (ease-out-quart t)
(let ((t* (- t 1.0)))
(- 1.0 (* t* t* t* t*))))
(define-inlinable (ease-in-out-quart t)
(if (< t 0.5)
(* 8.0 t t t t)
(let ((t* (- t 1.0)))
(- 1.0 (* 8.0 t* t* t* t*)))))
(define-inlinable (ease-in-quint t)
(* t t t t t))
(define-inlinable (ease-out-quint t)
(let ((t* (- t 1.0)))
(+ 1.0 (* t* t* t* t* t*))))
(define-inlinable (ease-in-out-quint t)
(if (< t 0.5)
(* 16.0 t t t t t)
(let ((t* (- t 1.0)))
(+ 1.0 (* 16.0 t* t* t* t* t*)))))
(define-inlinable (ease-in-sine t)
(+ (* (- t) (cos (* t pi/2))) t))
(define-inlinable (ease-out-sine t)
(* t (sin (* t pi/2))))
(define-inlinable (ease-in-out-sine t)
(* (/ t -2)
(1- (cos (* t pi)))))
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