using System;

namespace Science.Mathematics.LinearAlgebra
{
	/// <summary>
	/// Vector
	/// </summary>
	public class Vector
	{
		private int s;
		public int Size
		{
			get{return s;}
		}
		private double[] el;
		public Vector(int dimension)
		{
            s = dimension;
            el = new double[s];
		}
		public Vector(double[] x)
		{
			s = x.Length;
			el = new double[s];
			for(int k = 0; k < s; k++) el[k] = x[k];
		}
		public double this[int where]
		{
			get{return el[where];}
			set{el[where]=value;}
		}

		public double Norm
        {
            get
            {
                double sq = 0.0;
                foreach (double k in el) sq += k * k;
                return Math.Sqrt(sq);
            }
        }
        public double Length
        {
            get { return this.Norm; }           
        }

		public static Vector operator *(double a, Vector c)
		{
			Vector b = new Vector(c.Size);
			for(int k = 0; k < c.Size; k++) b[k] = a*c[k];
			return b;
		}  
		public static Vector operator *(Vector c, double a)
		{
			return a*c;
		}
		public static Vector operator +(Vector a, Vector c)
		{
			Vector b = new Vector(a.Size);
			for(int k = 0; k < a.Size; k++) b[k] = a[k] + c[k];
	    	return b;
		}
		public static Vector operator -(Vector a, Vector c)
		{
			Vector b = new Vector(a.Size);
			for(int k = 0; k < a.Size; k++) b[k] = a[k] - c[k];
            return b;
		}
        public static Vector operator -(Vector c)
        {
            Vector b = new Vector(c.Size);
            for (int k = 0; k < c.Size; k++)
                b[k] = -c[k];
            return b;
        }
		public static double operator *(Vector a, Vector c)
		{
			double sum = 0.0;
			for(int k = 0; k < a.Size; k++) sum += a[k]*c[k];
			return sum;
		}
		public static Vector operator %(Vector a, Vector c)  // CrossProduct in only Length = 3 Real Vector
		{
			Vector b = new Vector(3);
			b[0] = a[1]*c[2]-a[2]*c[1];
			b[1] = a[2]*c[0]-a[0]*c[2];
			b[2] = a[0]*c[1]-a[1]*c[0];
			return b;
		}

        public void Chop()
        {
            for (int k = 0; k < s; k++)
            {
                if (el[k] < 0.00000001 && el[k] > -0.00000001) el[k] = 0.0;
            }
        }

        public override string ToString()
        {
            string res = "";
            for (int i = 0; i < this.Size; i++)
            {
                res += this[i].ToString() + "\r\n";              
            }
            return res;
        }
	}
}