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/*
 * Copyright 1998-2014 University Corporation for Atmospheric Research/Unidata
 *
 *   Portions of this software were developed by the Unidata Program at the
 *   University Corporation for Atmospheric Research.
 *
 *   Access and use of this software shall impose the following obligations
 *   and understandings on the user. The user is granted the right, without
 *   any fee or cost, to use, copy, modify, alter, enhance and distribute
 *   this software, and any derivative works thereof, and its supporting
 *   documentation for any purpose whatsoever, provided that this entire
 *   notice appears in all copies of the software, derivative works and
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 *   software or in any product that includes this software. The names UCAR
 *   and/or Unidata, however, may not be used in any advertising or publicity
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 *   IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
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 *   WITH THE ACCESS, USE OR PERFORMANCE OF THIS SOFTWARE.
 */
package ucar.unidata.util;

import java.lang.ArithmeticException;


import java.lang.Math;

/**
 * Special Math functions.
 * Recoded from online sources for licensing purposes.
 * caron 6/22/2012
 */


public final class SpecialMathFunction {
  private static final double log2 = Math.log(2);

  /**
   * Get the log base 2 of a number
   * @param x a double value
   * @return The log₂ of x
   * @throws ArithmeticException if (x < 0)
   */
  static public double log2(double x) throws ArithmeticException {
    if (x <= 0.0) throw new ArithmeticException("range exception");
    return Math.log(x) / log2;
  }

  static public double atanh(double x) throws ArithmeticException {
    if ((x > 1.0) || (x < -1.0)) {
      throw new ArithmeticException("range exception");
    }
    return 0.5 * Math.log((1.0 + x) / (1.0 - x));
  }
}