Code cleanup.

Assets/Cryville/Common/Pdt/PdtEvaluatorBase.cs

@@ -127,7 +127,6 @@ namespace Cryville.Common.Pdt {
 		/// <returns>An operator of the specific name.</returns>
 		/// <remarks>The parameter count of the returned operator does not necessarily equal to <paramref name="pc" />.</remarks>
 		protected abstract PdtOperator GetOperator(string name, int pc);
-		bool _failure;
 		unsafe void Operate(PdtOperator op, int pc, bool noset = false) {
 			fixed (byte* pmem = _mem) {
 				op.Begin(this);

Assets/Cryville/Common/Pdt/PdtVariableMemory.cs

@@ -1,13 +1,11 @@
 using System;
-using System.Text;
-using UnityEditor;
 
 namespace Cryville.Common.Pdt {
 	/// <summary>
 	/// Span on the memory of a <see cref="PdtEvaluatorBase" />.
 	/// </summary>
 	public unsafe struct PdtVariableMemory {
-		byte* _ptr;
+		readonly byte* _ptr;
 		/// <summary>
 		/// The length of the span.
 		/// </summary>