Sample Code Entry

From Henkelman Group

The purpose of this page is to demonstrate how you might use the wiki to explain or share your code. I am using an n-dimensional Vector class I made in Java for this example.

This describes the package the Vector class belongs to.

package CompChem.Geometry;

This is the definition of the Vector class in Java.

public class Vector
{

elements holds each of the vector elements, while dimension stores the number of elements in the vector.

    public double[] elements;
    public int dimension;

This is the constructor - it takes an array of doubles to use as the vector elements.

    public Vector(double[] _elements)
    {
	elements = _elements.clone();
	dimension = elements.length;
    }

This clones the Vector object - don't worry about this if you're not yet familiar with completely referenced languages like Java.

    public Vector clone()
    {
	Vector r = new Vector(elements.clone());
	return r;
    }

This returns the magnitude of the vector.

    public double magnitude()
    {
	double sum = 0;
	for(int i = 0; i < dimension; i++)
	{
	    sum += elements[i] * elements[i];
       }
	return Math.sqrt(sum);
    }

This returns a new Vector that is the result of a scaling operation on the vector calling this function: Vector V = v.mul(2) would make V twice the size of v.

    public Vector mul(double scale)
    {
	Vector r = clone();
	for(int i = 0; i < dimension; i++)
	{
	    r.elements[i] *= scale;
	}
	return r;
    }

This returns the dot product of two vectors: Vector V = a.dot(b) would make V = a dot b.

    public double dot(Vector b)
    {
	if(dimension != b.dimension)
	{
	    return 0;
	}
	double sum = 0;
	for(int i = 0; i < dimension; i++)
	{
	    sum += elements[i] * b.elements[i];
	}
	return sum;
    }

This returns a Vector that is the sum of two vectors: Vector V = a.plus(b) would make V = a + b.

    public Vector plus(Vector b)
    {
	if(dimension != b.dimension)
	{
	    return null;
	}
	double[] r = new double[dimension];
	for(int i = 0; i < dimension; i++)
	{
	    r[i] = elements[i] + b.elements[i];
	}
	return new Vector(r);
    }

Opposite of plus: Vector V = a.minus(b) would make V = a - b.

    public Vector minus(Vector b)
    {
	if(dimension != b.dimension)
	{
	    return null;
	}
	double[] r = new double[dimension];
	for(int i = 0; i < dimension; i++)
	{
	    r[i] = elements[i] - b.elements[i];
	}
	return new Vector(r);
    }

Close the class definition.

}