C# implementation of Robert Penner's easing functions

Easing.cs

// TERMS OF USE - EASING EQUATIONS
// 
// Open source under the BSD License. 
// 
// Copyright © 2001 Robert Penner
// All rights reserved.
// 
// Redistribution and use in source and binary forms, with or without modification, are permitted provided that the following conditions are met:
// 
// Redistributions of source code must retain the above copyright notice, this list of conditions and the following disclaimer.
// Redistributions in binary form must reproduce the above copyright notice, this list of conditions and the following disclaimer in the documentation and/or other materials provided with the distribution.
// Neither the name of the author nor the names of contributors may be used to endorse or promote products derived from this software without specific prior written permission.
// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

using System;

namespace Easing
{
    // Arguments:
    // t - current time
    // b - beginning (initial) value
    // c - change (delta) value (same units as b)
    // d - duration (same units as t)
    // s - (optional) ??
    // a - (optional) wave amplitude
    // p - (optional) wave period
    //
    // Example:
    //     // A generator that takes 5 seconds to raise a position by 10m.
    //     IEnumerator Lift(Vector3 position)
    //     {
    //         float b = position.y; // use input initial position
    //         float c = 10f;        // move up 10 m
    //         float d = 5f;         // moving for 5 seconds
    //         for (float t = 0f; t < d; t += Time.deltaTime)
    //         {
    //             position.y = Back.In(t, b, c, d);
    //             yield return null;
    //         }
    //     }


    public static class Back
    {
        public static float In(float t, float b, float c, float d)
        {
            float s = 1.70158f;
            return c * (t /= d) * t * ((s + 1) * t - s) + b;
        }

        public static float In(float t, float b, float c, float d, float s)
        {
            return c * (t /= d) * t * ((s + 1) * t - s) + b;
        }

        public static float Out(float t, float b, float c, float d)
        {
            float s = 1.70158f;
            return c * ((t = t / d - 1) * t * ((s + 1) * t + s) + 1) + b;
        }

        public static float Out(float t, float b, float c, float d, float s)
        {
            return c * ((t = t / d - 1) * t * ((s + 1) * t + s) + 1) + b;
        }

        public static float InOut(float t, float b, float c, float d)
        {
            float s = 1.70158f;
            if ((t /= d / 2) < 1) return c * 0.5 * (t * t * (((s *= (1.525f)) + 1) * t - s)) + b;
            return c * 0.5 * ((t -= 2) * t * (((s *= (1.525f)) + 1) * t + s) + 2) + b;
        }

        public static float InOut(float t, float b, float c, float d, float s)
        {
            if ((t /= d / 2) < 1) return c * 0.5 * (t * t * (((s *= (1.525f)) + 1) * t - s)) + b;
            return c * 0.5 * ((t -= 2) * t * (((s *= (1.525f)) + 1) * t + s) + 2) + b;
        }
    }

    public static class Bounce
    {
        public static float In(float t, float b, float c, float d)
        {
            return c - Out(d - t, 0, c, d) + b;
        }

        public static float Out(float t, float b, float c, float d)
        {
            if ((t /= d) < (1 / 2.75f))
            {
                return c * (7.5625f * t * t) + b;
            }
            else if (t < (2 / 2.75f))
            {
                return c * (7.5625f * (t -= (1.5f / 2.75f)) * t + .75f) + b;
            }
            else if (t < (2.5 / 2.75))
            {
                return c * (7.5625f * (t -= (2.25f / 2.75f)) * t + .9375f) + b;
            }
            else {
                return c * (7.5625f * (t -= (2.625f / 2.75f)) * t + .984375f) + b;
            }
        }

        public static float InOut(float t, float b, float c, float d)
        {
            if (t < d / 2) return In(t * 2, 0, c, d) * .5f + b;
            else return Out(t * 2 - d, 0, c, d) * .5f + c * .5f + b;
        }
    }

    public static class Circ
    {
        public static float In(float t, float b, float c, float d)
        {
            return -c * ((float)Math.Sqrt(1 - (t /= d) * t) - 1) + b;
        }

        public static float Out(float t, float b, float c, float d)
        {
            return c * (float)Math.Sqrt(1 - (t = t / d - 1) * t) + b;
        }

        public static float InOut(float t, float b, float c, float d)
        {
            if ((t /= d / 2) < 1) return -c / 2 * ((float)Math.Sqrt(1 - t * t) - 1) + b;
            return c * 0.5 * ((float)Math.Sqrt(1 - (t -= 2) * t) + 1) + b;
        }
    }

    public static class Cubic
    {
        public static float In(float t, float b, float c, float d)
        {
            return c * (t /= d) * t * t + b;
        }

        public static float Out(float t, float b, float c, float d)
        {
            return c * ((t = t / d - 1) * t * t + 1) + b;
        }

        public static float InOut(float t, float b, float c, float d)
        {
            if ((t /= d / 2) < 1) return c * 0.5 * t * t * t + b;
            return c * 0.5 * ((t -= 2) * t * t + 2) + b;
        }
    }

    public static class Elastic
    {
        public static float In(float t, float b, float c, float d)
        {
            if (t == 0) return b; if ((t /= d) == 1) return b + c;
            float p = d * .3f;
            float a = c;
            float s = p / 4;
            return -(a * (float)Math.Pow(2, 10 * (t -= 1)) * (float)Math.Sin((t * d - s) * (2 * (float)Math.PI) / p)) + b;
        }

        public static float In(float t, float b, float c, float d, float a, float p)
        {
            float s;
            if (t == 0) return b; if ((t /= d) == 1) return b + c;
            if (a < Math.Abs(c)) { a = c; s = p / 4; }
            else { s = p / (2 * (float)Math.PI) * (float)Math.Asin(c / a); }
            return -(a * (float)Math.Pow(2, 10 * (t -= 1)) * (float)Math.Sin((t * d - s) * (2 * Math.PI) / p)) + b;
        }

        public static float Out(float t, float b, float c, float d)
        {
            if (t == 0) return b; if ((t /= d) == 1) return b + c;
            float p = d * .3f;
            float a = c;
            float s = p / 4;
            return (a * (float)Math.Pow(2, -10 * t) * (float)Math.Sin((t * d - s) * (2 * (float)Math.PI) / p) + c + b);
        }

        public static float Out(float t, float b, float c, float d, float a, float p)
        {
            float s;
            if (t == 0) return b; if ((t /= d) == 1) return b + c;
            if (a < Math.Abs(c)) { a = c; s = p / 4; }
            else { s = p / (2 * (float)Math.PI) * (float)Math.Asin(c / a); }
            return (a * (float)Math.Pow(2, -10 * t) * (float)Math.Sin((t * d - s) * (2 * (float)Math.PI) / p) + c + b);
        }

        public static float InOut(float t, float b, float c, float d)
        {
            if (t == 0) return b; if ((t /= d / 2) == 2) return b + c;
            float p = d * (.3f * 1.5f);
            float a = c;
            float s = p / 4;
            if (t < 1) return -.5f * (a * (float)Math.Pow(2, 10 * (t -= 1)) * (float)Math.Sin((t * d - s) * (2 * (float)Math.PI) / p)) + b;
            return a * (float)Math.Pow(2, -10 * (t -= 1)) * (float)Math.Sin((t * d - s) * (2 * (float)Math.PI) / p) * .5f + c + b;
        }

        public static float InOut(float t, float b, float c, float d, float a, float p)
        {
            float s;
            if (t == 0) return b; if ((t /= d / 2) == 2) return b + c;
            if (a < Math.Abs(c)) { a = c; s = p / 4; }
            else { s = p / (2 * (float)Math.PI) * (float)Math.Asin(c / a); }
            if (t < 1) return -.5f * (a * (float)Math.Pow(2, 10 * (t -= 1)) * (float)Math.Sin((t * d - s) * (2 * (float)Math.PI) / p)) + b;
            return a * (float)Math.Pow(2, -10 * (t -= 1)) * (float)Math.Sin((t * d - s) * (2 * (float)Math.PI) / p) * .5f + c + b;
        }
    }

    public static class Expo
    {
        public static float In(float t, float b, float c, float d)
        {
            return (t == 0) ? b : c * (float)Math.Pow(2, 10 * (t / d - 1)) + b;
        }

        public static float Out(float t, float b, float c, float d)
        {
            return (t == d) ? b + c : c * (-(float)Math.Pow(2, -10 * t / d) + 1) + b;
        }

        public static float InOut(float t, float b, float c, float d)
        {
            if (t == 0) return b;
            if (t == d) return b + c;
            if ((t /= d / 2) < 1) return c * 0.5 * (float)Math.Pow(2, 10 * (t - 1)) + b;
            return c * 0.5 * (-(float)Math.Pow(2, -10 * --t) + 2) + b;
        }
    }

    public static class Linear
    {
        public static float None(float t, float b, float c, float d)
        {
            return c * t / d + b;
        }

        public static float In(float t, float b, float c, float d)
        {
            return c * t / d + b;
        }

        public static float Out(float t, float b, float c, float d)
        {
            return c * t / d + b;
        }

        public static float InOut(float t, float b, float c, float d)
        {
            return c * t / d + b;
        }
    }

    public static class Quad
    {
        public static float In(float t, float b, float c, float d)
        {
            return c * (t /= d) * t + b;
        }

        public static float Out(float t, float b, float c, float d)
        {
            return -c * (t /= d) * (t - 2) + b;
        }

        public static float InOut(float t, float b, float c, float d)
        {
            if ((t /= d / 2) < 1) return c * 0.5 * t * t + b;
            return -c / 2 * ((--t) * (t - 2) - 1) + b;
        }
    }

    public static class Quart
    {
        public static float In(float t, float b, float c, float d)
        {
            return c * (t /= d) * t * t * t + b;
        }

        public static float Out(float t, float b, float c, float d)
        {
            return -c * ((t = t / d - 1) * t * t * t - 1) + b;
        }

        public static float InOut(float t, float b, float c, float d)
        {
            if ((t /= d / 2) < 1) return c * 0.5 * t * t * t * t + b;
            return -c / 2 * ((t -= 2) * t * t * t - 2) + b;
        }
    }

    public static class Quint
    {
        public static float In(float t, float b, float c, float d)
        {
            return c * (t /= d) * t * t * t * t + b;
        }

        public static float Out(float t, float b, float c, float d)
        {
            return c * ((t = t / d - 1) * t * t * t * t + 1) + b;
        }

        public static float InOut(float t, float b, float c, float d)
        {
            if ((t /= d / 2) < 1) return c * 0.5 * t * t * t * t * t + b;
            return c * 0.5 * ((t -= 2) * t * t * t * t + 2) + b;
        }
    }

    public static class Sine
    {
        public static float In(float t, float b, float c, float d)
        {
            return -c * (float)Math.Cos(t / d * (Math.PI / 2)) + c + b;
        }

        public static float Out(float t, float b, float c, float d)
        {
            return c * (float)Math.Sin(t / d * (Math.PI / 2)) + b;
        }

        public static float InOut(float t, float b, float c, float d)
        {
            return -c / 2 * ((float)Math.Cos(Math.PI * t / d) - 1) + b;
        }
    }
}