diff --git a/AlgebraicDataflowArchitectureModel/src/models/algebra/Constant.java b/AlgebraicDataflowArchitectureModel/src/models/algebra/Constant.java
index cc1ffee..5f533a7 100644
--- a/AlgebraicDataflowArchitectureModel/src/models/algebra/Constant.java
+++ b/AlgebraicDataflowArchitectureModel/src/models/algebra/Constant.java
@@ -36,7 +36,7 @@
 	
 	public String toImplementation(String[] sideEffects) {
 		if (symbol.isImplGenerative()) {
-			String exp = symbol.generate(getType(), new String[] {}, new String[] {}, sideEffects);
+			String exp = symbol.generate(getType(), new Type[] {}, new String[] {}, new String[] {}, sideEffects);
 			return exp;
 		}
 		return symbol.getImplName();
diff --git a/AlgebraicDataflowArchitectureModel/src/models/algebra/Symbol.java b/AlgebraicDataflowArchitectureModel/src/models/algebra/Symbol.java
index 8c8c974..ad03b97 100644
--- a/AlgebraicDataflowArchitectureModel/src/models/algebra/Symbol.java
+++ b/AlgebraicDataflowArchitectureModel/src/models/algebra/Symbol.java
@@ -161,14 +161,15 @@
 	/**
 	 * Generate the implementation of this symbol
 	 * @param type the type of this symbol
+	 * @param childrenTypes the types of the children expressions
 	 * @param childrenImpl the implementations of the children
 	 * @param childrenSideEffects (input) an array of the side effects of the children
 	 * @param sideEffect (output) an array of the side effect of this symbol
 	 * @return the implementation
 	 */
-	public String generate(models.algebra.Type type, String[] childrenImpl, String[] childrenSideEffects, String[] sideEffect) {
+	public String generate(models.algebra.Type type, models.algebra.Type[] childrenTypes, String[] childrenImpl, String[] childrenSideEffects, String[] sideEffect) {
 		if (generator != null) {
-			return generator.generate(type, childrenImpl, childrenSideEffects, sideEffect);
+			return generator.generate(type, childrenTypes, childrenImpl, childrenSideEffects, sideEffect);
 		}
 		return null;
 	}
@@ -225,11 +226,12 @@
 		/**
 		 * Generate the implementation
 		 * @param type the type of this expression
-		 * @param children the implementations of the children
+		 * @param childrenTypes the types of the children expressions
+		 * @param childrenImpl the implementations of the children
 		 * @param childrenSideEffects (input) an array of the side effects of the children
 		 * @param sideEffect (output) an array of the side effect of this generator
 		 * @return the generated implementation
 		 */
-		public String generate(models.algebra.Type type, String children[], String[] childrenSideEffects, String[] sideEffect);
+		public String generate(models.algebra.Type type, models.algebra.Type[] childrenTypes, String childrenImpl[], String[] childrenSideEffects, String[] sideEffect);
 	}
 }
diff --git a/AlgebraicDataflowArchitectureModel/src/models/algebra/Term.java b/AlgebraicDataflowArchitectureModel/src/models/algebra/Term.java
index 3c15d21..e78c106 100644
--- a/AlgebraicDataflowArchitectureModel/src/models/algebra/Term.java
+++ b/AlgebraicDataflowArchitectureModel/src/models/algebra/Term.java
@@ -290,15 +290,22 @@
 			return exp;
 		}
 		if (symbol.isImplGenerative()) {
+			Type childrenTypes[] = new Type[children.size()];
 			String childrenImpl[] = new String[children.size()];
 			String childrenSideEffects[] = new String[children.size()];
 			if (implParamOrder == null) {
 				for (int i = 0; i < children.size(); i++) {
+					Expression child = children.get(i);
+					if (child instanceof Variable) {
+						childrenTypes[i] = ((Variable) child).getType();
+					} else if (child instanceof Term) {
+						childrenTypes[i] = ((Term) child).getType();
+					}
 					String childSideEffect[] = new String[] {""};
 					childrenImpl[i] = children.get(i).toImplementation(childSideEffect);
 					childrenSideEffects[i] = childSideEffect[0];
 				}
-				String exp = symbol.generate(getType(), childrenImpl, childrenSideEffects, sideEffects);
+				String exp = symbol.generate(getType(), childrenTypes, childrenImpl, childrenSideEffects, sideEffects);
 				if (symbol.isImplWithSideEffect()) {
 					sideEffects[0] = sideEffects[0] + exp;
 					exp = children.get(0).toImplementation(new String[] {""});	// the value of this term
@@ -306,11 +313,17 @@
 				return exp;
 			} else {
 				for (int i = 0; i < children.size(); i++) {
+					Expression child = children.get(implParamOrder[i]);
+					if (child instanceof Variable) {
+						childrenTypes[i] = ((Variable) child).getType();
+					} else if (child instanceof Term) {
+						childrenTypes[i] = ((Term) child).getType();
+					}
 					String childSideEffect[] = new String[] {""};
 					childrenImpl[i] = children.get(implParamOrder[i]).toImplementation(childSideEffect);
 					childrenSideEffects[i] = childSideEffect[0];
 				}
-				String exp = symbol.generate(getType(), childrenImpl, childrenSideEffects, sideEffects);
+				String exp = symbol.generate(getType(), childrenTypes, childrenImpl, childrenSideEffects, sideEffects);
 				if (symbol.isImplWithSideEffect()) {
 					sideEffects[0] = sideEffects[0] + exp;
 					exp = children.get(implParamOrder[0]).toImplementation(new String[] {""});	// the value of this term
diff --git a/AlgebraicDataflowArchitectureModel/src/models/dataConstraintModel/DataConstraintModel.java b/AlgebraicDataflowArchitectureModel/src/models/dataConstraintModel/DataConstraintModel.java
index 7eac780..e6b2936 100644
--- a/AlgebraicDataflowArchitectureModel/src/models/dataConstraintModel/DataConstraintModel.java
+++ b/AlgebraicDataflowArchitectureModel/src/models/dataConstraintModel/DataConstraintModel.java
@@ -47,10 +47,21 @@
 	public static final Symbol length = new Symbol("length", 1, Symbol.Type.PREFIX, "($x)->$x.size()", Symbol.Type.LAMBDA);
 	public static final Symbol get = new Symbol("get", 2, Symbol.Type.PREFIX, "get", Symbol.Type.METHOD);
 	public static final Symbol set = new Symbol("set", 3, Symbol.Type.PREFIX, "set", Symbol.Type.METHOD_WITH_SIDE_EFFECT);
-	public static final Symbol contains = new Symbol("contains", 2, Symbol.Type.PREFIX, "contains", Symbol.Type.METHOD);
+	public static final Symbol contains = new Symbol("contains", 2, Symbol.Type.PREFIX, new Symbol.IImplGenerator() {
+		@Override
+		public String generate(Type type, Type[] childrenTypes, String[] childrenImpl, String[] childrenSideEffects, String[] sideEffect) {
+			for (String s: childrenSideEffects) {
+				sideEffect[0] += s;
+			}
+			if (childrenTypes[0] != null && (typeMap.isAncestorOf(childrenTypes[0]) || typeJson.isAncestorOf(childrenTypes[0]))) {
+				return childrenImpl[0] + "." + "containsKey(" + childrenImpl[1] + ")";
+			}
+			return childrenImpl[0] + "." + "contains(" + childrenImpl[1] + ")";
+		}
+	});
 	public static final Symbol nil = new Symbol("nil", 0, Symbol.Type.PREFIX, new Symbol.IImplGenerator() {
 		@Override
-		public String generate(Type type, String[] children, String[] childrenSideEffects, String[] sideEffect) {
+		public String generate(Type type, Type[] childrenTypes, String[] childrenImpl, String[] childrenSideEffects, String[] sideEffect) {
 			String compType = "";
 			if (type != null) {
 				String temp = "temp_nil";
@@ -72,18 +83,18 @@
 	public static final Symbol cond = new Symbol("if", 3, Symbol.Type.PREFIX, new Symbol.IImplGenerator() {
 		final int count[] = {0};
 		@Override
-		public String generate(Type type, String[] children, String[] childrenSideEffects, String[] sideEffect) {
+		public String generate(Type type, Type[] childrenTypes, String[] childrenImpl, String[] childrenSideEffects, String[] sideEffect) {
 			String temp = "temp_if" + count[0];
 			String impl = ""; 
 			
 			impl += type.getInterfaceTypeName() + " " + temp + ";\n";
 			if (childrenSideEffects[0] != null && childrenSideEffects[0].length() > 0) impl += childrenSideEffects[0];
-			impl += "if (" + children[0] + ") {\n";
+			impl += "if (" + childrenImpl[0] + ") {\n";
 			if (childrenSideEffects[1] != null && childrenSideEffects[1].length() > 0) impl += "\t" + childrenSideEffects[1];
-			impl += "\t" + temp + " = " + children[1] + ";\n";
+			impl += "\t" + temp + " = " + childrenImpl[1] + ";\n";
 			impl += "} else {\n";
 			if (childrenSideEffects[2] != null && childrenSideEffects[2].length() > 0) impl += "\t" + childrenSideEffects[2];
-			impl += "\t" + temp + " = " + children[2] + ";\n";
+			impl += "\t" + temp + " = " + childrenImpl[2] + ";\n";
 			impl += "}\n";
 			
 			sideEffect[0] += impl;
@@ -108,7 +119,7 @@
 	public static final Symbol false_ = new Symbol("false", 0, Symbol.Type.PREFIX, "false", Symbol.Type.PREFIX);
 	public static final Symbol pair = new Symbol("pair", -1, Symbol.Type.PREFIX, new Symbol.IImplGenerator() {
 		@Override
-		public String generate(Type type, String[] childrenImpl, String[] childrenSideEffects, String[] sideEffect) {
+		public String generate(Type type, Type[] childrenTypes, String[] childrenImpl, String[] childrenSideEffects, String[] sideEffect) {
 			for (String s: childrenSideEffects) {
 				sideEffect[0] += s;
 			}
@@ -118,7 +129,7 @@
 	});
 	public static final Symbol tuple = new Symbol("tuple", -1, Symbol.Type.PREFIX, new Symbol.IImplGenerator() {
 		@Override
-		public String generate(Type type, String[] childrenImpl, String[] childrenSideEffects, String[] sideEffect) {
+		public String generate(Type type, Type[] childrenTypes, String[] childrenImpl, String[] childrenSideEffects, String[] sideEffect) {
 			for (String s: childrenSideEffects) {
 				sideEffect[0] += s;
 			}
@@ -139,7 +150,7 @@
 	public static final Symbol lookup = new Symbol("lookup", 2, Symbol.Type.PREFIX, new Symbol.IImplGenerator() {
 		final int count[] = {0};
 		@Override
-		public String generate(Type type, String[] childrenImpl, String[] childrenSideEffects, String[] sideEffect) {
+		public String generate(Type type, Type[] childrenTypes, String[] childrenImpl, String[] childrenSideEffects, String[] sideEffect) {
 			String temp = "temp_get" + count[0];
 			String impl = childrenSideEffects[0] + childrenSideEffects[1];
 			impl += type.getInterfaceTypeName() + " " + temp + ";\n";
@@ -183,7 +194,7 @@
 		remove.setSignature(new Type[] {typeList, typeList, typeInt});
 		head.setSignature(new Type[] {null, typeList});
 		tail.setSignature(new Type[] {typeList, typeList});
-		contains.setSignature(new Type[] {typeBoolean, typeList, null});
+		contains.setSignature(new Type[] {typeBoolean, null, null});
 		length.setSignature(new Type[] {typeInt, null});
 		get.setSignature(new Type[] {null, typeList, typeInt});
 		set.setSignature(new Type[] {typeList, typeList, typeInt, null});
diff --git a/AlgebraicDataflowArchitectureModel/src/models/dataFlowModel/ModelExtension.java b/AlgebraicDataflowArchitectureModel/src/models/dataFlowModel/ModelExtension.java
index 54a5c98..8f6f36a 100644
--- a/AlgebraicDataflowArchitectureModel/src/models/dataFlowModel/ModelExtension.java
+++ b/AlgebraicDataflowArchitectureModel/src/models/dataFlowModel/ModelExtension.java
@@ -28,7 +28,7 @@
 			final int[] count = new int[] {0};
 			sum.setGenerator(new Symbol.IImplGenerator() {
 				@Override
-				public String generate(Type type, String[] children, String[] childrenSideEffects, String[] sideEffect) {
+				public String generate(Type type, Type[] childrenTypes, String[] childrenImpl, String[] childrenSideEffects, String[] sideEffect) {
 					String compType = "Integer";
 					if (type != null) {
 						String interfaceType = type.getInterfaceTypeName();
@@ -38,7 +38,7 @@
 					}
 					count[0]++;
 					String impl = compType + " " + "temp_sum" + count[0] + " = 0;\n";
-					impl += "for (" + compType + " x: " + children[0] + ") {\n";
+					impl += "for (" + compType + " x: " + childrenImpl[0] + ") {\n";
 					impl += "\t" + "temp_sum" + count[0] + " += x;\n";
 					impl += "}\n";
 					sideEffect[0] = sideEffect[0] + impl;
@@ -58,7 +58,7 @@
 			final int[] count = new int[] {0};
 			merge.setGenerator(new Symbol.IImplGenerator() {
 				@Override
-				public String generate(Type type, String[] childrenImpl, String[] childrenSideEffects, String[] sideEffect) {
+				public String generate(Type type, Type[] childrenTypes, String[] childrenImpl, String[] childrenSideEffects, String[] sideEffect) {
 					String implType = "ArrayList<>";
 					String interfaceType = "List<Integer>";
 					String compType = "Integer";
@@ -111,8 +111,8 @@
 			extractFaceDown.setArity(1);
 			extractFaceDown.setGenerator(new Symbol.IImplGenerator() {
 				@Override
-				public String generate(Type type, String[] children, String[] childrenSideEffects, String[] sideEffect) {			
-					return children[0]+".stream().filter(item -> item.getValue()==false).collect(Collectors.toList())";
+				public String generate(Type type, Type[] childrenTypes, String[] childrenImpl, String[] childrenSideEffects, String[] sideEffect) {			
+					return childrenImpl[0]+".stream().filter(item -> item.getValue()==false).collect(Collectors.toList())";
 				}
 			});
 			extractFaceDown.setImplOperatorType(Symbol.Type.GENERATIVE);
@@ -126,7 +126,7 @@
 			sortByKey.setArity(1);
 			sortByKey.setGenerator(new Symbol.IImplGenerator() {
 				@Override
-				public String generate(Type type, String[] children, String[] childrenSideEffects, String[] sideEffect) {			
+				public String generate(Type type, Type[] childrenTypes, String[] childrenImpl, String[] childrenSideEffects, String[] sideEffect) {			
 					String compType = "";
 					String temp_sort="temp_sort";
 					if (type != null) {
@@ -143,7 +143,7 @@
 					for (String s: childrenSideEffects) {
 						sideEffect[0] += s;
 					}
-					temp_sort=children[0]+".sort(Comparator.comparing("+compType+"::getKey));\n";
+					temp_sort=childrenImpl[0]+".sort(Comparator.comparing("+compType+"::getKey));\n";
 					return temp_sort;
 				}
 			});
@@ -159,7 +159,7 @@
 			selectGEMem = selectGE.createMemento();
 			selectGE.setGenerator(new Symbol.IImplGenerator() {
 				@Override
-				public String generate(Type type, String[] childrenImpl, String[] childrenSideEffects, String[] sideEffect) {			
+				public String generate(Type type, Type[] childrenTypes, String[] childrenImpl, String[] childrenSideEffects, String[] sideEffect) {			
 					String implType = "ArrayList<>";
 					String interfaceType = "List<Map<String, Object>>";
 					count[0]++;
@@ -188,7 +188,7 @@
 			selectLEMem = selectLE.createMemento();
 			selectLE.setGenerator(new Symbol.IImplGenerator() {
 				@Override
-				public String generate(Type type, String[] childrenImpl, String[] childrenSideEffects, String[] sideEffect) {			
+				public String generate(Type type, Type[] childrenTypes, String[] childrenImpl, String[] childrenSideEffects, String[] sideEffect) {			
 					String implType = "ArrayList<>";
 					String interfaceType = "List<Map<String, Object>>";
 					count[0]++;