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Program 4

using System;
using System.Collections;

public struct Interval{

  private readonly int from, to;
  private readonly bool empty;

  // Construct a non-empty interval [from - to] if empty is false.
  // Else construct an empty interval (from and to are not used). 
  private Interval(int from, int to, bool empty){
    this.empty = empty;
    this.from = from; = to;

  public static Interval MakeInterval(int from, int to){
    return new Interval(from,to,false);

  public static Interval MakeEmptyInterval(){
    return new Interval(0,0,true);

  // Other Interval operations not shown