TestYield.cs

using UnityEngine;
using System.Collections;
using System.Collections.Generic;

public class TestYield : MonoBehaviour 
{
    public void Start() {
        IntList list = new IntList();
        list.Add(3);
        list.Add(5);
        list.Add(7);

        printIntList(list);

        list[0] = 1;

        //printIntList(list);

        //for (int i = 0; i < 100; i++)
        //{
        //    list.Add(i);
        //}

        printIntList(list);
        
        
    }

    private void printIntList(IntList list)
    {
        //foreach (int i in list)
        //{
        //    Debug.Log(i);
        //}
        
        IEnumerator enumerator = list.GetEnumerator();
        while (enumerator.MoveNext()) {
            object curr = enumerator.Current;
            Debug.Log(curr);
        }
    }


    class IntList : IEnumerable {
        static readonly int INITIAL_SLOTS = 10;
        int[] values = new int[INITIAL_SLOTS];
        int next = 0;

        public void Add(int value) 
        {
            values[next++] = value;
            if (next >= values.Length) {
                Expand();
            }
        }
        public int Get(int index) 
        {
            if (index >= next || index < 0) throw new System.ArgumentException();
            return values[index];
        }

        public void Set(int index, int value) {
            if (index > next || index < 0) throw new System.ArgumentException();
            values[index] = value;
        }

        public int this[int index] 
        {
            get { return Get(index); }
            set { Set(index, value);  }
        }

        private void Expand() 
        {
            int[] newValues = new int[values.Length * 2];
            for (int i = 0; i < values.Length; i++)
            {
                newValues[i] = values[i];
            }
            values = newValues;
        }
        public int Count { get { return next; } }

        public IEnumerator GetEnumerator()
        {
            //return new IntListEnum(this);
            for (int i = 0; i < next; i++)
            {
                yield return values[i];
            }
            
        }

        public class IntListEnum : IEnumerator
        {
            int index = -1;
            IntList list;

            public IntListEnum(IntList list) 
            {
                this.list = list;
            }
            object IEnumerator.Current { 
                get {
                    try
                    {
                        return list.values[index];
                    }
                    catch (System.ArgumentOutOfRangeException)
                    {
                        return new System.InvalidOperationException();
                    }
                } 
            }

            public bool MoveNext()
            {
                index++;
                if (index >= list.Count)
                {
                    return false;
                }
                else 
                {
                    return true;
                }
            }

            public void Reset()
            {
                index = -1;
            }
        }
    }
}