package jsci.maths.vectors;

import jsci.GlobalSettings;
import jsci.maths.Mapping;
import jsci.maths.MathDouble;
import jsci.maths.MathInteger;
import jsci.maths.algebras.Module;
import jsci.maths.algebras.VectorSpace;
import jsci.maths.fields.Field;
import jsci.maths.fields.Ring;
import jsci.maths.groups.AbelianGroup;
import jsci.maths.matrices.DoubleSparseMatrix;

/**
* The DoubleSparseVector class encapsulates sparse vectors.
* Uses Morse-coding.
* @author Daniel Lemire
* @author Alain Beliveau
*/
public final class DoubleSparseVector extends AbstractDoubleVector {
        private double vector[];
        /**
        * Sparse indexing data.
        * Contains the component positions of each element,
        * e.g. pos[n] is the component position
        * of the nth element
        * (the pos[n]th component is stored at index n).
        */
        private int pos[];
        /**
        * Constructs an empty vector.
        * @param dim the dimension of the vector.
        */
        public DoubleSparseVector(final int dim) {
                super(dim);
                vector=new double[0];
                pos=new int[0];
        }
        /**
        * Constructs a vector from an array.
        */
        public DoubleSparseVector(double array[]) {
                super(array.length);
                int n=0;
                for(int i=0;i=N)
                        throw new VectorDimensionException(getInvalidComponentMsg(n));
                for(int k=0;k=N)
                        throw new VectorDimensionException(getInvalidComponentMsg(n));
                if(Math.abs(x)<=GlobalSettings.ZERO_TOL)
                        return;
                for(int k=0;k2-norm (magnitude).
        */
        public double norm() {
                return Math.sqrt(sumSquares());
        }
        /**
        * Returns the sum of the squares of the components.
        */
        public double sumSquares() {
                double norm=0.0;
  		for(int k=0;k