diff --git a/AlgebraicDataflowArchitectureModel/src/models/algebra/Symbol.java b/AlgebraicDataflowArchitectureModel/src/models/algebra/Symbol.java
index 047f906..20c3cf2 100644
--- a/AlgebraicDataflowArchitectureModel/src/models/algebra/Symbol.java
+++ b/AlgebraicDataflowArchitectureModel/src/models/algebra/Symbol.java
@@ -210,7 +210,7 @@
 		return (calculator != null);
 	}
 	
-	public Constant calculate(List<Constant> args) {
+	public Expression calculate(List<Expression> args) {
 		if (calculator != null) {
 			return calculator.calculate(args);
 		}
@@ -279,6 +279,6 @@
 	}
 	
 	public interface ICalculator {
-		public Constant calculate(List<Constant> args);
+		public Expression calculate(List<Expression> args);
 	}
 }