Adds Unary length operator

Upsilon/BaseTypes/UserData/DictionaryUserData.cs

@@ -1,10 +1,13 @@
 using System.Collections;
+using System.Collections.Generic;
+using Upsilon.BaseTypes.Number;
+using Upsilon.BaseTypes.ScriptTypeInterfaces;
 using Upsilon.Evaluator;
 using Upsilon.Text;
 
 namespace Upsilon.BaseTypes.UserData
 {
-    internal class DictionaryUserData : ScriptType, IUserData
+    internal class DictionaryUserData : ScriptType, IUserData, ILengthType
     {
         public IDictionary Dictionary { get; }
 
@@ -47,5 +50,10 @@ namespace Upsilon.BaseTypes.UserData
         {
             return Dictionary.GetType();
         }
+
+        public ScriptNumberLong Length()
+        {
+            return new ScriptNumberLong(Dictionary.Count);
+        }
     }
 }

Upsilon/BaseTypes/UserData/ListUserData.cs

@@ -8,7 +8,7 @@ using Upsilon.Text;
 
 namespace Upsilon.BaseTypes.UserData
 {
-    internal class ListUserData : ScriptType, IUserData, IIterable
+    internal class ListUserData : ScriptType, IUserData, IIterable, ILengthType
     {
         private IList List { get; }
 
@@ -66,5 +66,10 @@ namespace Upsilon.BaseTypes.UserData
                 yield return new ScriptNumberLong(i);
             }
         }
+
+        public ScriptNumberLong Length()
+        {
+            return new ScriptNumberLong(List.Count);
+        }
     }
 }