- Add functions

- Code improvements

YesNt.Interpreter/Utilities/StringExtentions.cs

@@ -0,0 +1,53 @@
+using System;
+using System.Globalization;
+using System.Text;
+
+namespace YesNt.Interpreter.Utilities
+{
+    public static class StringExtentions
+    {
+        public static string ToSaveString(this string input)
+        {
+            StringBuilder output = new StringBuilder();
+            foreach (char c in input)
+            {
+                output.Append($"\r{c}\r");
+            }
+            return output.ToString();
+        }
+
+        public static string FromSaveString(this string input)
+        {
+            return input.Replace("\r", "");
+        }
+
+        public static bool ToStandardizedNumber(this string input, out double result)
+        {
+            return double.TryParse(input.FromSaveString().Replace(',', '.'), NumberStyles.Any, CultureInfo.InvariantCulture, out result);
+        }
+
+        public static string ReplaceFirstOccurrence(this string input, string oldValue, string newValue)
+        {
+            int place = input.IndexOf(oldValue);
+            return input.Remove(place, oldValue.Length).Insert(place, newValue);
+        }
+
+        public static string ReplaceLastOccurrence(this string input, string oldValue, string newValue)
+        {
+            int place = input.LastIndexOf(oldValue);
+            return input.Remove(place, Math.Min(oldValue.Length, input.Length - place)).Insert(place, newValue);
+        }
+
+        public static int WhiteSpaceAtEnd(this string input)
+        {
+            int count = 0;
+            int index = input.Length - 1;
+            while (index >= 0 && char.IsWhiteSpace(input[index--]))
+            {
+                count++;
+            }
+
+            return count;
+        }
+    }
+}