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//  The ASF licenses this file to You under the Apache License, Version 2.0
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//
//      http://www.apache.org/licenses/LICENSE-2.0
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package mx.effects.easing
{

/**
 *  The Spark effects provided as of Flex 4 use classes which implement the 
 *  IEaser interface instead of the easing functions in classes like Quadratic for 
 *  the earlier Flex 3 effects. To achieve the same functionality of Quadratic, 
 *  create a Power instance with an <code>exponent</code> of 2 and set the 
 *  <code>easeInFraction</code> appropriately to get the desired result.
 */
[Alternative(replacement="spark.effects.easing.Power", since="4.0")]

/**
 *  The Quadratic class defines three easing functions to implement 
 *  quadratic motion with Flex effect classes. The acceleration of motion 
 *  for a Quadratic easing equation is slower than for a Cubic or Quartic easing equation.
 *
 *  For more information, see http://www.robertpenner.com/profmx.
 *  
 *  @langversion 3.0
 *  @playerversion Flash 9
 *  @playerversion AIR 1.1
 *  @productversion Flex 3
 */  
public class Quadratic
{
    include "../../core/Version.as";

    //--------------------------------------------------------------------------
    //
    //  Class methods
    //
    //--------------------------------------------------------------------------

    /**
     *  The <code>easeIn()</code> method starts motion from a zero velocity, 
     *  and then accelerates motion as it executes. 
     *
     *  @param t Specifies time.
     *
     *  @param b Specifies the initial position of a component.
     *
     *  @param c Specifies the total change in position of the component.
     *
     *  @param d Specifies the duration of the effect, in milliseconds.
     *
     *  @return Number corresponding to the position of the component.
     *  
     *  @langversion 3.0
     *  @playerversion Flash 9
     *  @playerversion AIR 1.1
     *  @productversion Flex 3
     */  
    public static function easeIn(t:Number, b:Number,
                                  c:Number, d:Number):Number
    {
        return c * (t /= d) * t + b;
    }

    /**
     *  The <code>easeOut()</code> method starts motion fast, 
     *  and then decelerates motion to a zero velocity as it executes. 
     *
     *  @param t Specifies time.
     *
     *  @param b Specifies the initial position of a component.
     *
     *  @param c Specifies the total change in position of the component.
     *
     *  @param d Specifies the duration of the effect, in milliseconds.
     *
     *  @return Number corresponding to the position of the component.
     *  
     *  @langversion 3.0
     *  @playerversion Flash 9
     *  @playerversion AIR 1.1
     *  @productversion Flex 3
     */  
    public static function easeOut(t:Number, b:Number,
                                   c:Number, d:Number):Number
    {
        return -c * (t /= d) * (t - 2) + b;
    }

    /**
     *  The <code>easeInOut()</code> method combines the motion
     *  of the <code>easeIn()</code> and <code>easeOut()</code> methods
     *  to start the motion from a zero velocity, 
     *  accelerate motion, then decelerate to a zero velocity. 
     *
     *  @param t Specifies time.
     *
     *  @param b Specifies the initial position of a component.
     *
     *  @param c Specifies the total change in position of the component.
     *
     *  @param d Specifies the duration of the effect, in milliseconds.
     *
     *  @return Number corresponding to the position of the component.
     *  
     *  @langversion 3.0
     *  @playerversion Flash 9
     *  @playerversion AIR 1.1
     *  @productversion Flex 3
     */  
    public static function easeInOut(t:Number, b:Number,
                                     c:Number, d:Number):Number
    {
        if ((t /= d / 2) < 1)
            return c / 2 * t * t + b;

        return -c / 2 * ((--t) * (t - 2) - 1) + b;
    }
}

}