Attempt to optimise memory by employing an IEnumerable.

SimpleTurtle/LSystemEngine.cs

@@ -1,8 +1,7 @@
 using System;
 using System.Collections.Generic;
 using System.IO;
-using System.Runtime.InteropServices;
-using System.Security.Policy;
+using System.Linq;
 
 namespace SBRL.Algorithms.LSystem
 {
@@ -49,7 +48,7 @@ namespace SBRL.Algorithms.LSystem
 			// Find all the current positions
 			foreach(Rule rule in rules)
 			{
-				List<int> positions = AllIndexesOf(CurrentGeneration, rule.Find);
+				IEnumerable<int> positions = AllIndexesOf(CurrentGeneration, rule.Find);
 				foreach (int pos in positions)
 					rulePositions.Add(new KeyValuePair<int, Rule>(pos, rule));
 			}
@@ -79,15 +78,14 @@ namespace SBRL.Algorithms.LSystem
 		/// <param name="str"></param>
 		/// <param name="value"></param>
 		/// <returns></returns>
-		private List<int> AllIndexesOf(string str, string value) {
+		private IEnumerable<int> AllIndexesOf(string str, string value) {
 			if (String.IsNullOrEmpty(value))
-				throw new ArgumentException("the string to find may not be empty", "value");
-			List<int> indexes = new List<int>();
-			for (int index = 0;; index += value.Length) {
+				throw new ArgumentException("the string to find may not be empty", nameof(value));
+			for (int index = 0; ; index += value.Length) {
 				index = str.IndexOf(value, index);
 				if (index == -1)
-					return indexes;
-				indexes.Add(index);
+					break;
+				yield return index;
 			}
 		}