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/*
 * Copyright (c) 2016 Jacob Rachiele
 *
 * Permission is hereby granted, free of charge, to any person obtaining a copy of this software
 * and associated documentation files (the "Software"), to deal in the Software without restriction
 * including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense
 * and/or sell copies of the Software, and to permit persons to whom the Software is furnished to
 * do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included in all copies or
 * substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED
 * INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR
 * PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
 * LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT,
 * TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE
 * USE OR OTHER DEALINGS IN THE SOFTWARE.
 *
 * Contributors:
 *
 * Jacob Rachiele
 */
package math.function;

import optim.NumericalDerivatives;

/**
 * A partial implementation of a scalar-valued function of one variable.
 *
 */
public abstract class AbstractFunction implements Function {

  protected int functionEvaluations = 0;
  protected int slopeEvaluations = 0;
  
  /**
   * Compute and the return the slope at the given point.
   * @param point an element of the function's domain.
   * @return the slope of the function at the given point.
   */
  public double slopeAt(final double point) {
    slopeEvaluations++;
    return NumericalDerivatives.centralDifferenceApproximation(this, point, 1E-3);
  }

  public double slopeAt(final double point, final double functionValue) {
    slopeEvaluations++;
    return NumericalDerivatives.forwardDifferenceApproximation(this, point, 1E-6, functionValue);
  }
  
  /**
   * The number of times this function has been evaluated.
   *
   * @return the number of times this function has been evaluated.
   */
  public int functionEvaluations() {
    return this.functionEvaluations;
  }
  
  /**
   * The number of times the slope has been computed.
   *
   * @return the number of times the slope has been computed.
   */
  public int slopeEvaluations() {
    return this.slopeEvaluations;
  }
}