private string GetConditionString (Expr e)
		{
			var vSource = new SourcePositionVisitor (this.instructionLookup);
			vSource.Visit (e);
			var extractor = new ConditionTextExtractor (vSource.SourceCodeFileName, vSource.StartPosition, vSource.EndPosition);
			return extractor.GetConditionText ();
		}
		public ConditionTextExtractor (string filename, SourcePositionVisitor.CodePosition start, SourcePositionVisitor.CodePosition end)
		{
			this.filename = filename;
			this.start = start;
			this.end = end;
		}