package joptima.functions;

import joptima.Parameter;

/**
 * Function a * x + b.
 * A concrete implementation of joptima.Function that calculates
 * a linear function of one argument.
 */
public class Linear extends ConstrainableFunction {

  public double m_a, m_b;

  public Parameter[] getParameters() {
    Parameter[] parameters = new Parameter[countUnconstrained()];
    try {
      int cursor = 0;
      if (!m_constrained[0]) parameters[cursor++] = new Parameter(this, "a");
      if (!m_constrained[1]) parameters[cursor++] = new Parameter(this, "b");
    } catch (NoSuchFieldException nsfe) {
      nsfe.printStackTrace();
    }
    return parameters;
  }

  public void constrain(String parametername) {
    if ("a".equals(parametername)) m_constrained[0] = true;
    if ("b".equals(parametername)) m_constrained[1] = true;
  }

  private String m_name = "Linear";
  public String getName() { return m_name; }
  public void setName(String newname) { m_name = newname; }

  /**
   * Default constructor: a = 1, b = 0.
   */
  public Linear() {
    this(1, 0);
  }

  /**
   * Constructor.
   */
  public Linear(double a, double b) {
    this.m_a = a;
    this.m_b = b;
    m_constrained = new boolean[2];
  }

  public double calculate(double x) {
    return m_a * x + m_b;
  }

  public double getA() {
    return m_a;
  }

  public void setA(double a) {
    this.m_a = a;
  }

  public double getB() {
    return m_b;
  }

  public void setB(double b) {
    this.m_b = b;
  }
}