rootfunctions.java

来自「一个一元曲线多项式数值演示例子」· Java 代码 · 共 247 行

package numbercruncher.rootutils;

import java.util.*;

import numbercruncher.mathutils.*;

/**
 * Load into a global table the functions whose roots we want to find.
 */
public class RootFunctions {
  /** global function table */
  private static Hashtable TABLE = new Hashtable(32);

  // Enter the functions into the global function table.
  static {
    enterFunctions();
  }

  /**
   * Return the function with the given hash key
   * @param key the hash key
   * @return the function
   */
  public static Function function(String key) {
    return (Function) TABLE.get(key);
  }

  /**
   * Enter all the functions into the global function table.
   */
  private static void enterFunctions() {
    // Function f(x)  = x^2 - 4
    //          f'(x) = 2x
    TABLE.put(
        "x^2 - 4",
        new Function() {
      public float at(float x) {
        return x * x - 4;
      }

      public float derivativeAt(float x) {
        return 2 * x;
      }
    });

    // Function f(x)  = -x^2 + 4x + 5
    //          f'(x) = -2x + 4
    TABLE.put(
        "-x^2 + 4x + 5",
        new Function() {
      public float at(float x) {
        return -x * x + 4 * x + 5;
      }

      public float derivativeAt(float x) {
        return -2 * x + 4;
      }
    });

    // Function f(x)  = x^3 + 3x^2 - 9x - 10
    //          f'(x) = 3x^2 + 6x - 9
    TABLE.put(
        "x^3 + 3x^2 - 9x - 10",
        new Function() {
      public float at(float x) {
        return x * x * x + 3 * x * x - 9 * x - 10;
      }

      public float derivativeAt(float x) {
        return 3 * x * x + 6 * x - 9;
      }
    });

    // Function f(x)  = x^2 - 2x + 3
    //          f'(x) = 2x - 2
    TABLE.put(
        "x^2 - 2x + 3",
        new Function() {
      public float at(float x) {
        return x * x - 2 * x + 3;
      }

      public float derivativeAt(float x) {
        return 2 * x - 2;
      }
    });

    // Function f(x)  = 2x^3 - 10x^2 + 11x - 5
    //          f'(x) = 6x^2 - 20x + 11
    TABLE.put(
        "2x^3 - 10x^2 + 11x - 5",
        new Function() {
      public float at(float x) {
        return 2 * x * x * x - 10 * x * x + 11 * x - 5;
      }

      public float derivativeAt(float x) {
        return 6 * x * x - 20 * x + 11;
      }
    });

    // Function f(x)  = e^-x - x
    //          f'(x) = -e^-x - 1
    TABLE.put(
        "e^-x - x",
        new Function() {
      public float at(float x) {
        return ( (float) Math.exp( -x)) - x;
      }

      public float derivativeAt(float x) {
        return (float) - Math.exp( -x) - 1;
      }
    });

    // Function f(x)  = x - e^(1/x)
    //          f'(x) = 1 + (1/x^2)e^(1/x)
    TABLE.put(
        "x - e^(1/x)",
        new Function() {
      public float at(float x) {
        return x - ( (float) Math.exp(1 / x));
      }

      public float derivativeAt(float x) {
        return 1 + (1 / (x * x)) * ( (float) Math.exp(1 / x));
      }
    });

    // Function g(x) = (x + 4/x)/2
    TABLE.put(
        "(x + 4/x)/2",
        new Function() {
      public float at(float x) {
        return (x + 4 / x) / 2;
      }
    });

    // Function g(x) = 4/x
    TABLE.put(
        "4/x",
        new Function() {
      public float at(float x) {
        return 4 / x;
      }
    });

    // Function g(x) = sqrt(x + 2)
    TABLE.put(
        "sqrt(x + 2)",
        new Function() {
      public float at(float x) {
        return (float) Math.sqrt(x + 2);
      }
    });

    // Function g(x) = 2/x + 1
    TABLE.put(
        "2/x + 1",
        new Function() {
      public float at(float x) {
        return 2 / x + 1;
      }
    });

    // Function g(x) = x^2 - 2
    TABLE.put(
        "x*x - 2",
        new Function() {
      public float at(float x) {
        return x * x - 2;
      }
    });

    // Function g(x) = e^-x
    TABLE.put(
        "exp(-x)",
        new Function() {
      public float at(float x) {
        return (float) Math.exp( -x);
      }
    });

    // Function g(x) = -ln(x)
    TABLE.put(
        "-log(x)",
        new Function() {
      public float at(float x) {
        return (float) - Math.log(x);
      }
    });

    // Function g(x) = e^(1/x)
    TABLE.put(
        "exp(1/x)",
        new Function() {
      public float at(float x) {
        return (float) Math.exp(1 / x);
      }
    });

    // Function g(x) = (x + e^(1/x))/2
    TABLE.put(
        "(x + exp(1/x))/2",
        new Function() {
      public float at(float x) {
        return (x + ( (float) Math.exp(1 / x))) / 2;
      }
    });

    // Function g(x) = 1/ln(x)
    TABLE.put(
        "1/log(x)",
        new Function() {
      public float at(float x) {
        return 1 / ( (float) Math.log(x));
      }
    });

    // Function g(x) = sin(x)/2 + 1
    TABLE.put(
        "sin(x)/2 + 1",
        new Function() {
      public float at(float x) {
        return ( (float) Math.sin(x) / 2) + 1;
      }
    });

    // Function g(x) = 1 + 1/x + 1/x^2
    TABLE.put(
        "1 + 1/x + 1/(x*x)",
        new Function() {
      public float at(float x) {
        return 1 + 1 / x + 1 / (x * x);
      }
    });

    // Function g(x) = 20/(x^2 + 2x + 10)
    TABLE.put(
        "20/(x*x + 2*x + 10)",
        new Function() {
      public float at(float x) {
        return 20 / (x * x + 2 * x + 10);
      }
    });
  }
}