Pull down EvaluationFailureException.

Assets/Cryville/Common/Pdt/PdtEvaluatorBase.cs

@@ -1,5 +1,6 @@
 using System;
 using System.Collections.Generic;
+using System.Runtime.Serialization;
 
 namespace Cryville.Common.Pdt {
 	/// <summary>
@@ -167,10 +168,10 @@ namespace Cryville.Common.Pdt {
 		internal void Operate(PdtOperatorSignature sig) {
 			PdtOperator op;
 			try { op = GetOperator(sig); }
-			catch (Exception) {
+			catch (Exception ex) {
 				for (int i = 0; i < sig.ParamCount; i++)
 					DiscardStack();
-				throw;
+				throw new EvaluationFailureException(string.Format("Failed to get operator {0}", sig), ex);
 			}
 			Operate(op, sig.ParamCount);
 		}
@@ -222,4 +223,18 @@ namespace Cryville.Common.Pdt {
 			_goffset -= _stack[--_framecount].Length;
 		}
 	}
+
+	/// <summary>
+	/// The exception that is thrown when the evalution of a <see cref="PdtExpression" /> fails.
+	/// </summary>
+	public class EvaluationFailureException : Exception {
+		/// <inheritdoc />
+		public EvaluationFailureException() : base("Evaluation failed") { }
+		/// <inheritdoc />
+		public EvaluationFailureException(string message) : base(message) { }
+		/// <inheritdoc />
+		public EvaluationFailureException(string message, Exception innerException) : base(message, innerException) { }
+		/// <inheritdoc />
+		protected EvaluationFailureException(SerializationInfo info, StreamingContext context) : base(info, context) { }
+	}
 }