Nullable variable

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using System;
using System.Collections.Generic;
using System.Text;

public class Vector {
public double? R = null;
public double? Theta = null;

public double? ThetaRadians {
get {
return (Theta * Math.PI / 180.0);
}
}

public Vector(double? r, double? theta) {
if (r < 0) { r = -r; theta += 180; } theta = theta % 360; R = r; Theta = theta; } public static Vector operator +(Vector op1, Vector op2) { try { double newX = op1.R.Value * Math.Sin(op1.ThetaRadians.Value) + op2.R.Value * Math.Sin(op2.ThetaRadians.Value); double newY = op1.R.Value * Math.Cos(op1.ThetaRadians.Value) + op2.R.Value * Math.Cos(op2.ThetaRadians.Value); double newR = Math.Sqrt(newX * newX + newY * newY); double newTheta = Math.Atan2(newX, newY) * 180.0 / Math.PI; return new Vector(newR, newTheta); } catch { return new Vector(null, null); } } public static Vector operator -(Vector op1) { return new Vector(-op1.R, op1.Theta); } public static Vector operator -(Vector op1, Vector op2) { return op1 + (-op2); } public override string ToString() { string rString = R.HasValue ? R.ToString() : "null"; string thetaString = Theta.HasValue ? Theta.ToString() : "null"; return string.Format("({0}, {1})", rString, thetaString); } } class Program { public static void Main(string[] args) { Vector v1 = GetVector("vector1"); Vector v2 = GetVector("vector1"); Console.WriteLine("{0} + {1} = {2}", v1, v2, v1 + v2); Console.WriteLine("{0} - {1} = {2}", v1, v2, v1 - v2); Console.ReadKey(); } public static Vector GetVector(string name) { Console.WriteLine("Input {0} magnitude:", name); double? r = GetNullableDouble(); Console.WriteLine("Input {0} angle (in degrees):", name); double? theta = GetNullableDouble(); return new Vector(r, theta); } public static double? GetNullableDouble() { double? result; string userInput = Console.ReadLine(); try { result = double.Parse(userInput); } catch { result = null; } return result; } } [/csharp]

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