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Unit Standard (JSR 363) Reference Implementation.
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/*
 * Units of Measurement Reference Implementation
 * Copyright (c) 2005-2016, Jean-Marie Dautelle, Werner Keil, V2COM.
 *
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without modification,
 * are permitted provided that the following conditions are met:
 *
 * 1. Redistributions of source code must retain the above copyright notice,
 *    this list of conditions and the following disclaimer.
 *
 * 2. 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.
 *
 * 3. Neither the name of JSR-363 nor the names of its 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 HOLDER 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.
 */
package tec.units.ri.function;

import tec.units.ri.AbstractConverter;
import tec.uom.lib.common.function.ValueSupplier;

/**
 * 
 * This class represents a converter multiplying numeric values by π (Pi).
 * 
 * 
 * @see  Wikipedia: Pi
 * @author Jean-Marie Dautelle
 * @author Werner Keil
 * @version 0.4, December 28, 2015
 */
public final class PiMultiplierConverter extends AbstractConverter implements ValueSupplier {

  /**
   * Creates a Pi multiplier converter.
   */
  public PiMultiplierConverter() {
  }

  @Override
  public double convert(double value) {
    return value * PI;
  }

  // @Override
  // public BigDecimal convert(BigDecimal value, MathContext ctx)
  // throws ArithmeticException {
  // int nbrDigits = ctx.getPrecision();
  // if (nbrDigits == 0)
  // throw new ArithmeticException(
  // "Pi multiplication with unlimited precision");
  // BigDecimal pi = Pi.pi(nbrDigits);
  // return value.multiply(pi, ctx).scaleByPowerOfTen(1 - nbrDigits);
  // }
  @Override
  public AbstractConverter inverse() {
    return new PiDivisorConverter();
  }

  @Override
  public final String toString() {
    return "(π)";
  }

  @Override
  public boolean equals(Object obj) {
    return (obj instanceof PiMultiplierConverter);
  }

  @Override
  public int hashCode() {
    return 0;
  }

  public boolean isLinear() {
    return true;
  }

  /**
   * Pi calculation with Machin's formula.
   * 
   * @see Pi with Machin's formula
   * 
   */
  // static final class Pi {
  //
  // private Pi() {
  // }
  //
  // public static Double pi(int numDigits) {
  // int calcDigits = numDigits + 10;
  // return 4 * ((4 * (arccot(5, calcDigits))) - arccot(239, calcDigits)); /*
  // * )
  // * .
  // * setScale
  // * (
  // * numDigits
  // * ,
  // * RoundingMode
  // * .
  // * DOWN
  // * )
  // * ;
  // */
  // }
  //
  // private static double arccot(double x, int numDigits) {
  // double unity = 1; /*
  // * BigDecimal.ONE.setScale(numDigits,
  // * RoundingMode.DOWN);
  // */
  // double sum = unity / x;
  // double xpower = sum;
  // Double term = null;
  // boolean add = false;
  // for (double n = 3; term == null || !term.equals(Double.valueOf(0)); n += 2) {
  // xpower = xpower / ((long) x ^ 2);
  // term = xpower / n;
  // sum = add ? sum + term : sum - term;
  // add = !add;
  // }
  // return sum;
  // }
  // }
  // private static final BigDecimal TWO = new BigDecimal("2");
  // private static final BigDecimal FOUR = new BigDecimal("4");
  // private static final BigDecimal FIVE = new BigDecimal("5");
  // private static final BigDecimal TWO_THIRTY_NINE = new BigDecimal("239");
  public String getValue() {
    return toString();
  }
}