diff --git a/AlgebraicDataflowArchitectureModel/src/algorithms/JavaMethodBodyGenerator.java b/AlgebraicDataflowArchitectureModel/src/algorithms/JavaMethodBodyGenerator.java
index 5d55493..d061f00 100644
--- a/AlgebraicDataflowArchitectureModel/src/algorithms/JavaMethodBodyGenerator.java
+++ b/AlgebraicDataflowArchitectureModel/src/algorithms/JavaMethodBodyGenerator.java
@@ -16,6 +16,7 @@
 import models.algebra.ParameterizedIdentifierIsFutureWork;
 import models.algebra.Symbol;
 import models.algebra.Term;
+import models.algebra.Type;
 import models.algebra.UnificationFailed;
 import models.algebra.ValueUndefined;
 import models.algebra.Variable;
@@ -46,8 +47,80 @@
 		Symbol.Memento sumMem = null;
 		if (sum != null) {
 			sumMem = sum.createMemento();
-			sum.setImplName("stream().mapToInt(x->x).sum");
-			sum.setImplOperatorType(Symbol.Type.METHOD);
+			final int[] count = new int[] {0};
+			sum.setGenerator(new Symbol.IImplGenerator() {
+				@Override
+				public String generate(Type type, String[] children, String[] sideEffects) {
+					String compType = "Integer";
+					if (type != null) {
+						String interfaceType = type.getInterfaceTypeName();
+						if (interfaceType.contains("<")) {
+							compType = interfaceType.substring(interfaceType.indexOf("<") + 1, interfaceType.lastIndexOf(">"));
+						}						
+					}
+					count[0]++;
+					String impl = compType + " " + "temp_sum" + count[0] + " = 0;\n";
+					impl += "for (" + compType + " x: " + children[0] + ") {\n";
+					impl += "\t" + "temp_sum" + count[0] + " += x;\n";
+					impl += "}\n";
+					sideEffects[0] = sideEffects[0] + impl;
+					return "temp_sum" + count[0];
+				}
+			});
+			sum.setImplOperatorType(Symbol.Type.GENERATIVE);
+//			sum.setImplName("stream().mapToInt(x->x).sum");
+//			sum.setImplOperatorType(Symbol.Type.METHOD);
+		}
+		Symbol merge = model.getSymbol("merge");
+		Symbol.Memento mergeMem = null;
+		if (merge != null) {
+			mergeMem = merge.createMemento();
+			merge.setArity(2);
+			final int[] count = new int[] {0};
+			merge.setGenerator(new Symbol.IImplGenerator() {
+				@Override
+				public String generate(Type type, String[] childrenImpl, String[] sideEffects) {
+					String implType = "Arrayist<>";
+					String interfaceType = "List<Integer>";
+					String compType = "Integer";
+					if (type != null) {
+						implType = type.getImplementationTypeName();
+						interfaceType = type.getInterfaceTypeName();
+						if (interfaceType.contains("<")) {
+							compType = interfaceType.substring(interfaceType.indexOf("<") + 1, interfaceType.lastIndexOf(">"));
+						}
+					}
+					String idxGetter = "";
+					if (compType.startsWith("AbstractMap.SimpleEntry")) {
+						idxGetter = ".getKey()";
+					}
+					count[0]++;
+					String impl = "";
+					impl += "" + interfaceType + " temp_l" + count[0] + " = new " + implType + "();\n";
+					impl += "Iterator<" + compType + "> i1 = " + childrenImpl[0] + ".iterator();\n";
+					impl += "Iterator<" + compType + "> i2 = " + childrenImpl[1] + ".iterator();\n";
+					impl += compType + " t1 = null;\n";
+					impl += compType + " t2 = null;\n";
+					impl += "while (i1.hasNext() || i2.hasNext()) {\n";
+					impl += "\tif (t1 == null && i1.hasNext()) {\n";
+					impl += "\t\tt1 = i1.next();\n";
+					impl += "\t}\n";
+					impl += "\tif (t2 == null && i2.hasNext()) {\n";
+					impl += "\t\tt2 = i2.next();\n";
+					impl += "\t}\n";
+					impl += "\tif (t1 == null || (t2 != null && t1" + idxGetter + " > t2" + idxGetter + ")) {\n";
+					impl += "\t\ttemp_l"  + count[0] +".add(t2);\n";
+					impl += "\t\tt2 = null;\n";
+					impl += "\t} else {\n";
+					impl += "\t\ttemp_l" + count[0] + ".add(t1);\n";
+					impl += "\t\tt1 = null;\n";
+					impl += "\t}\n";
+					impl += "}\n";
+					sideEffects[0] = sideEffects[0] + impl;
+					return "temp_l" + count[0];
+				}
+			});
+			merge.setImplOperatorType(Symbol.Type.GENERATIVE);
 		}
 
 		// Create a map from type names (lower case) to their types.
@@ -77,12 +150,13 @@
 							if (((StoreAttribute) dst.getAttribute()).isStored()) {
 								// update stored state of dst resource (when every incoming edge is in push style)
 								Expression updateExp = d.getChannelGenerator().deriveUpdateExpressionOf(out, JavaCodeGenerator.pushAccessor);
-								String curState = updateExp.toImplementation();
+								String[] sideEffects = new String[] {""};
+								String curState = updateExp.toImplementation(sideEffects);
 								String updateStatement;
 								if (updateExp instanceof Term && ((Term) updateExp).getSymbol().isImplWithSideEffect()) {
-									updateStatement = curState + ";";								
+									updateStatement = sideEffects[0];
 								} else {
-									updateStatement = dstResourceName + " = " + curState + ";";
+									updateStatement = sideEffects[0] + dstResourceName + " = " + curState + ";";
 								}
 								if (update.getBody() == null || !update.getBody().getStatements().contains(updateStatement)) {
 									update.addFirstStatement(updateStatement);
@@ -123,14 +197,15 @@
 										inputIdentifierToStateAccessor.put(((ResourceNode) dIn.getSource()).getIdentifierTemplate(), JavaCodeGenerator.pullAccessor);
 									}
 								}
+								String[] sideEffects = new String[] {""};
 								if (!isContainedPush) {
 									// All incoming edges are in PULL style.
-									String curState = d.getChannelGenerator().deriveUpdateExpressionOf(out, JavaCodeGenerator.pullAccessor).toImplementation();
-									getter.addStatement("return " + curState + ";");
+									String curState = d.getChannelGenerator().deriveUpdateExpressionOf(out, JavaCodeGenerator.pullAccessor).toImplementation(sideEffects);
+									getter.addStatement(sideEffects[0] + "return " + curState + ";");
 								} else {
 									// At least one incoming edge is in PUSH style.
-									String curState = d.getChannelGenerator().deriveUpdateExpressionOf(out, JavaCodeGenerator.pullAccessor, inputIdentifierToStateAccessor).toImplementation();
-									getter.addStatement("return " + curState + ";");
+									String curState = d.getChannelGenerator().deriveUpdateExpressionOf(out, JavaCodeGenerator.pullAccessor, inputIdentifierToStateAccessor).toImplementation(sideEffects);
+									getter.addStatement(sideEffects[0] + "return " + curState + ";");
 								}
 							}
 						} 
@@ -157,13 +232,14 @@
 						Term message = (Term) out.getStateTransition().getMessageExpression();
 						MethodDeclaration input = getMethod(type, message.getSymbol().getName());
 						if (input != null) {
+							String[] sideEffects = new String[] {""};
 							Expression updateExp = ioChannelAndMember.getKey().deriveUpdateExpressionOf(out, JavaCodeGenerator.pushAccessor);
-							String newState = updateExp.toImplementation();
+							String newState = updateExp.toImplementation(sideEffects);
 							String updateStatement;
 							if (updateExp instanceof Term && ((Term) updateExp).getSymbol().isImplWithSideEffect()) {
-								updateStatement = newState + ";";								
+								updateStatement = sideEffects[0];	
 							} else {
-								updateStatement = "this." + resourceName + " = " + newState + ";";
+								updateStatement = sideEffects[0] + "this." + resourceName + " = " + newState + ";";
 							}
 							if (input.getBody() == null || !input.getBody().getStatements().contains(updateStatement)) {
 								input.addFirstStatement(updateStatement);
@@ -191,6 +267,7 @@
 		
 		if (floor != null) floor.setMemento(floorMem);
 		if (sum != null) sum.setMemento(sumMem);
+		if (merge != null) merge.setMemento(mergeMem);
 		return codes;
 	}
 
diff --git a/AlgebraicDataflowArchitectureModel/src/algorithms/JerseyMethodBodyGenerator.java b/AlgebraicDataflowArchitectureModel/src/algorithms/JerseyMethodBodyGenerator.java
index ff6e7de..ee6d6de 100644
--- a/AlgebraicDataflowArchitectureModel/src/algorithms/JerseyMethodBodyGenerator.java
+++ b/AlgebraicDataflowArchitectureModel/src/algorithms/JerseyMethodBodyGenerator.java
@@ -49,8 +49,80 @@
 		Symbol.Memento sumMem = null;
 		if (sum != null) {
 			sumMem = sum.createMemento();
-			sum.setImplName("stream().mapToInt(x->x).sum");
-			sum.setImplOperatorType(Symbol.Type.METHOD);
+			final int[] count = new int[] {0};
+			sum.setGenerator(new Symbol.IImplGenerator() {
+				@Override
+				public String generate(Type type, String[] children, String[] sideEffects) {
+					String compType = "Integer";
+					if (type != null) {
+						String interfaceType = type.getInterfaceTypeName();
+						if (interfaceType.contains("<")) {
+							compType = interfaceType.substring(interfaceType.indexOf("<") + 1, interfaceType.lastIndexOf(">"));
+						}						
+					}
+					count[0]++;
+					String impl = compType + " " + "temp_sum" + count[0] + " = 0;\n";
+					impl += "for (" + compType + " x: " + children[0] + ") {\n";
+					impl += "\t" + "temp_sum" + count[0] + " += x;\n";
+					impl += "}\n";
+					sideEffects[0] = sideEffects[0] + impl;
+					return "temp_sum" + count[0];
+				}
+			});
+			sum.setImplOperatorType(Symbol.Type.GENERATIVE);
+//			sum.setImplName("stream().mapToInt(x->x).sum");
+//			sum.setImplOperatorType(Symbol.Type.METHOD);
+		}
+		Symbol merge = model.getSymbol("merge");
+		Symbol.Memento mergeMem = null;
+		if (merge != null) {
+			mergeMem = merge.createMemento();
+			merge.setArity(2);
+			final int[] count = new int[] {0};
+			merge.setGenerator(new Symbol.IImplGenerator() {
+				@Override
+				public String generate(Type type, String[] childrenImpl, String[] sideEffects) {
+					String implType = "Arrayist<>";
+					String interfaceType = "List<Integer>";
+					String compType = "Integer";
+					if (type != null) {
+						implType = type.getImplementationTypeName();
+						interfaceType = type.getInterfaceTypeName();
+						if (interfaceType.contains("<")) {
+							compType = interfaceType.substring(interfaceType.indexOf("<") + 1, interfaceType.lastIndexOf(">"));
+						}
+					}
+					String idxGetter = "";
+					if (compType.startsWith("AbstractMap.SimpleEntry")) {
+						idxGetter = ".getKey()";
+					}
+					count[0]++;
+					String impl = "";
+					impl += "" + interfaceType + " temp_l" + count[0] + " = new " + implType + "();\n";
+					impl += "Iterator<" + compType + "> i1 = " + childrenImpl[0] + ".iterator();\n";
+					impl += "Iterator<" + compType + "> i2 = " + childrenImpl[1] + ".iterator();\n";
+					impl += compType + " t1 = null;\n";
+					impl += compType + " t2 = null;\n";
+					impl += "while (i1.hasNext() || i2.hasNext()) {\n";
+					impl += "\tif (t1 == null && i1.hasNext()) {\n";
+					impl += "\t\tt1 = i1.next();\n";
+					impl += "\t}\n";
+					impl += "\tif (t2 == null && i2.hasNext()) {\n";
+					impl += "\t\tt2 = i2.next();\n";
+					impl += "\t}\n";
+					impl += "\tif (t1 == null || (t2 != null && t1" + idxGetter + " > t2" + idxGetter + ")) {\n";
+					impl += "\t\ttemp_l"  + count[0] +".add(t2);\n";
+					impl += "\t\tt2 = null;\n";
+					impl += "\t} else {\n";
+					impl += "\t\ttemp_l" + count[0] + ".add(t1);\n";
+					impl += "\t\tt1 = null;\n";
+					impl += "\t}\n";
+					impl += "}\n";
+					sideEffects[0] = sideEffects[0] + impl;
+					return "temp_l" + count[0];
+				}
+			});
+			merge.setImplOperatorType(Symbol.Type.GENERATIVE);
 		}
 
 		// Create a map from type names (lower case) to their types.
@@ -81,12 +153,13 @@
 							if (((StoreAttribute) dst.getAttribute()).isStored()) {
 								// update stored state of dst resource (when every incoming edge is in push style)
 								Expression updateExp = d.getChannelGenerator().deriveUpdateExpressionOf(out, JerseyCodeGenerator.pushAccessor);
-								String curState = updateExp.toImplementation();
+								String[] sideEffects = new String[] {""};
+								String curState = updateExp.toImplementation(sideEffects);
 								String updateStatement;
 								if (updateExp instanceof Term && ((Term) updateExp).getSymbol().isImplWithSideEffect()) {
-									updateStatement = curState + ";";								
+									updateStatement = sideEffects[0];								
 								} else {
-									updateStatement = dstResourceName + " = " + curState + ";";
+									updateStatement = sideEffects[0] + dstResourceName + " = " + curState + ";";
 								}
 								if (update.getBody() == null || !update.getBody().getStatements().contains(updateStatement)) {
 									update.addFirstStatement(updateStatement);
@@ -146,8 +219,9 @@
 							// for pull (or push/pull) data transfer
 							MethodDeclaration getter = getGetterMethod(dstType);
 							if (getter.getBody() == null || getter.getBody().getStatements().size() == 0) {
-								String curState = d.getChannelGenerator().deriveUpdateExpressionOf(out, JerseyCodeGenerator.pullAccessor).toImplementation();
-								getter.addStatement("return " + curState + ";");
+								String[] sideEffects = new String[] {""};
+								String curState = d.getChannelGenerator().deriveUpdateExpressionOf(out, JerseyCodeGenerator.pullAccessor).toImplementation(sideEffects);
+								getter.addStatement(sideEffects[0] + "return " + curState + ";");
 							}
 							getter.addFirstStatement(getHttpMethodCallStatement(baseURL, srcResourceName, "get", src.getIdentifierTemplate().getResourceStateType()));
 						} 
@@ -173,12 +247,13 @@
 						MethodDeclaration input = getMethod(type, message.getSymbol().getName());
 						if (input != null) {
 							Expression updateExp = ioChannelAndMember.getKey().deriveUpdateExpressionOf(out, JerseyCodeGenerator.pushAccessor);
-							String newState = updateExp.toImplementation();
+							String[] sideEffects = new String[] {""};
+							String newState = updateExp.toImplementation(sideEffects);
 							String updateStatement;
 							if (updateExp instanceof Term && ((Term) updateExp).getSymbol().isImplWithSideEffect()) {
-								updateStatement = newState + ";";								
+								updateStatement = sideEffects[0];								
 							} else {
-								updateStatement = "this." + resourceName + " = " + newState + ";";
+								updateStatement = sideEffects[0] + "this." + resourceName + " = " + newState + ";";
 							}
 							if (input.getBody() == null || !input.getBody().getStatements().contains(updateStatement)) {
 								input.addFirstStatement(updateStatement);
@@ -194,6 +269,7 @@
 		
 		if (floor != null) floor.setMemento(floorMem);
 		if (sum != null) sum.setMemento(sumMem);
+		if (merge != null) merge.setMemento(mergeMem);
 		return codes;
 	}
 
diff --git a/AlgebraicDataflowArchitectureModel/src/models/algebra/Constant.java b/AlgebraicDataflowArchitectureModel/src/models/algebra/Constant.java
index 1e698ed..023e28d 100644
--- a/AlgebraicDataflowArchitectureModel/src/models/algebra/Constant.java
+++ b/AlgebraicDataflowArchitectureModel/src/models/algebra/Constant.java
@@ -32,7 +32,7 @@
 		return symbol.getName();
 	}
 	
-	public String toImplementation() {
+	public String toImplementation(String[] sideEffects) {
 		return symbol.getImplName();
 	}
 }
diff --git a/AlgebraicDataflowArchitectureModel/src/models/algebra/Expression.java b/AlgebraicDataflowArchitectureModel/src/models/algebra/Expression.java
index a99f62b..872f54a 100644
--- a/AlgebraicDataflowArchitectureModel/src/models/algebra/Expression.java
+++ b/AlgebraicDataflowArchitectureModel/src/models/algebra/Expression.java
@@ -14,7 +14,7 @@
 		return getSubTerms(Variable.class);
 	}
 	
-	public String toImplementation() {
+	public String toImplementation(String[] sideEffects) {
 		return toString();
 	}
 }
diff --git a/AlgebraicDataflowArchitectureModel/src/models/algebra/Field.java b/AlgebraicDataflowArchitectureModel/src/models/algebra/Field.java
index c1af7f8..f51b3c4 100644
--- a/AlgebraicDataflowArchitectureModel/src/models/algebra/Field.java
+++ b/AlgebraicDataflowArchitectureModel/src/models/algebra/Field.java
@@ -39,7 +39,7 @@
 		return new Field(symbol);
 	}
 	
-	public String toImplementation() {
-		return "this." + super.toImplementation();
+	public String toImplementation(String[] sideEffects) {
+		return "this." + super.toImplementation(sideEffects);
 	}
 }
diff --git a/AlgebraicDataflowArchitectureModel/src/models/algebra/Symbol.java b/AlgebraicDataflowArchitectureModel/src/models/algebra/Symbol.java
index ac91474..9d7cc57 100644
--- a/AlgebraicDataflowArchitectureModel/src/models/algebra/Symbol.java
+++ b/AlgebraicDataflowArchitectureModel/src/models/algebra/Symbol.java
@@ -9,6 +9,7 @@
 	private Symbol[] inverses = null;
 	private models.algebra.Type[] signature = null;
 	private int[] implParamOrder = null;
+	private IImplGenerator generator = null;
 	
 	public Symbol(String name) {
 		this.name = name;
@@ -45,6 +46,26 @@
 		this.implParamOrder = implParamOrder;
 	}
 	
+	public Symbol(String name, int arity, Type operatorType, IImplGenerator generator) {
+		this.name = name;
+		this.arity = arity;
+		this.operatorType = operatorType;
+		this.generator = generator;
+		this.implOperatorType = Type.GENERATIVE;
+	}
+	
+	public Symbol(String name, int arity, Type operatorType, IImplGenerator generator, boolean bSideEffect) {
+		this.name = name;
+		this.arity = arity;
+		this.operatorType = operatorType;
+		this.generator = generator;
+		if (!bSideEffect) {
+			this.implOperatorType = Type.GENERATIVE;
+		} else {
+			this.implOperatorType = Type.GENERATIVE_WITH_SIDE_EFFECT;
+		}
+	}
+	
 	public void setArity(int arity) {
 		this.arity = arity;
 	}
@@ -109,8 +130,14 @@
 		return (implOperatorType == Type.LAMBDA || implOperatorType == Type.LAMBDA_WITH_SIDE_EFFECT);
 	}
 	
+	public boolean isImplGenerative() {
+		return (implOperatorType == Type.GENERATIVE || implOperatorType == Type.GENERATIVE_WITH_SIDE_EFFECT);
+	}
+	
 	public boolean isImplWithSideEffect() {
-		return (implOperatorType == Type.METHOD_WITH_SIDE_EFFECT || implOperatorType == Type.LAMBDA_WITH_SIDE_EFFECT);
+		return (implOperatorType == Type.METHOD_WITH_SIDE_EFFECT 
+				|| implOperatorType == Type.LAMBDA_WITH_SIDE_EFFECT 
+				|| implOperatorType == Type.GENERATIVE_WITH_SIDE_EFFECT);
 	}
 
 	public void setImplOperatorType(Type implOperatorType) {
@@ -120,6 +147,17 @@
 	public int[] getImplParamOrder() {
 		return implParamOrder;
 	}
+	
+	public void setGenerator(IImplGenerator generator) {
+		this.generator = generator; 
+	}
+	
+	public String generate(models.algebra.Type type, String[] childrenImpl, String[] sideEffects) {
+		if (generator != null) {
+			return generator.generate(type, childrenImpl, sideEffects);
+		}
+		return null;
+	}
 
 	public boolean equals(Object another) {
 		if (!(another instanceof Symbol)) return false;
@@ -145,7 +183,9 @@
 		METHOD,
 		METHOD_WITH_SIDE_EFFECT,
 		LAMBDA,
-		LAMBDA_WITH_SIDE_EFFECT
+		LAMBDA_WITH_SIDE_EFFECT,
+		GENERATIVE,
+		GENERATIVE_WITH_SIDE_EFFECT
 	}
 	
 	public Memento createMemento() {
@@ -166,4 +206,8 @@
 			this.implOperatorType = implOperatorType;
 		}
 	}
+	
+	public interface IImplGenerator {
+		public String generate(models.algebra.Type type, String children[], String[] sideEffects);
+	}
 }
diff --git a/AlgebraicDataflowArchitectureModel/src/models/algebra/Term.java b/AlgebraicDataflowArchitectureModel/src/models/algebra/Term.java
index d468d09..dc50323 100644
--- a/AlgebraicDataflowArchitectureModel/src/models/algebra/Term.java
+++ b/AlgebraicDataflowArchitectureModel/src/models/algebra/Term.java
@@ -206,7 +206,7 @@
 	}
 
 	
-	public String toImplementation() {
+	public String toImplementation(String[] sideEffects) {
 		int[] implParamOrder = symbol.getImplParamOrder();
 		if (symbol.isImplLambda()) {
 			String[] components = symbol.getImplName().split("->");
@@ -215,48 +215,90 @@
 			String exp = components[1];
 			if (implParamOrder == null) {
 				for (int i = 0; i < params.length; i++) {
-					exp = exp.replace(params[i], children.get(i).toImplementation());
+					exp = exp.replace(params[i], children.get(i).toImplementation(sideEffects));
 				}
 			} else {
 				for (int i = 0; i < params.length; i++) {
-					exp = exp.replace(params[i], children.get(implParamOrder[i]).toImplementation());
+					exp = exp.replace(params[i], children.get(implParamOrder[i]).toImplementation(sideEffects));
+				}
+			}
+			if (symbol.isImplWithSideEffect()) {
+				sideEffects[0] = sideEffects[0] + exp;
+				if (implParamOrder == null) {
+					exp = children.get(0).toImplementation(new String[] {""});
+				} else {
+					exp = children.get(implParamOrder[0]).toImplementation(new String[] {""});
 				}
 			}
 			return exp;
 		}
+		if (symbol.isImplGenerative()) {
+			String childrenImpl[] = new String[children.size()];
+			if (implParamOrder == null) {
+				for (int i = 0; i < children.size(); i++) {
+					childrenImpl[i] = children.get(i).toImplementation(sideEffects);
+				}
+				String exp =  symbol.generate(getType(), childrenImpl, sideEffects);
+				if (symbol.isImplWithSideEffect()) {
+					sideEffects[0] = sideEffects[0] + exp;
+					exp = children.get(0).toImplementation(new String[] {""});
+				}
+				return exp;
+			} else {
+				for (int i = 0; i < children.size(); i++) {
+					childrenImpl[i] = children.get(implParamOrder[i]).toImplementation(sideEffects);
+				}
+				String exp =  symbol.generate(getType(), childrenImpl, sideEffects);
+				if (symbol.isImplWithSideEffect()) {
+					sideEffects[0] = sideEffects[0] + exp;
+					exp = children.get(implParamOrder[0]).toImplementation(new String[] {""});
+				}
+				return exp;
+			}
+		}
 		if (getArity() == 2 && symbol.isImplInfix()) {
 			if (implParamOrder == null) {
-				return "(" + children.get(0).toImplementation() + symbol.toImplementation() + children.get(1).toImplementation() + ")";
+				return "(" + children.get(0).toImplementation(sideEffects) + symbol.toImplementation() + children.get(1).toImplementation(sideEffects) + ")";
 			} else {
-				return "(" + children.get(implParamOrder[0]).toImplementation() + symbol.toImplementation() + children.get(implParamOrder[1]).toImplementation() + ")";				
+				return "(" + children.get(implParamOrder[0]).toImplementation(sideEffects) + symbol.toImplementation() + children.get(implParamOrder[1]).toImplementation(sideEffects) + ")";				
 			}
 		}
 		if (getArity() >= 1 && symbol.isImplMethod()) {
 			if (implParamOrder == null) {
-				String exp = children.get(0).toImplementation() + "." + symbol.toImplementation() + "(";
+				String exp = children.get(0).toImplementation(sideEffects) + "." + symbol.toImplementation() + "(";
 				String delimiter = "";
 				for (int i = 1; i < children.size(); i++) {
 					Expression e = children.get(i);
-					exp += (delimiter + e.toImplementation());
+					exp += (delimiter + e.toImplementation(sideEffects));
 					delimiter = ",";
 				}
-				return exp + ")";
+				exp += ")";
+				if (symbol.isImplWithSideEffect()) {
+					sideEffects[0] = sideEffects[0] + exp;
+					exp = children.get(0).toImplementation(new String[] {""});
+				}
+				return exp;
 			} else {
-				String exp = children.get(implParamOrder[0]).toImplementation() + "." + symbol.toImplementation() + "(";
+				String exp = children.get(implParamOrder[0]).toImplementation(sideEffects) + "." + symbol.toImplementation() + "(";
 				String delimiter = "";
 				for (int i = 1; i < children.size(); i++) {
 					Expression e = children.get(implParamOrder[i]);
-					exp += (delimiter + e.toImplementation());
+					exp += (delimiter + e.toImplementation(sideEffects));
 					delimiter = ",";
 				}
-				return exp + ")";
+				exp += ")";
+				if (symbol.isImplWithSideEffect()) {
+					sideEffects[0] = sideEffects[0] + exp;
+					exp = children.get(implParamOrder[0]).toImplementation(new String[] {""});
+				}
+				return exp;
 			}
 		} else {
 			if (implParamOrder == null) {
 				String exp = symbol.toImplementation() + "(";
 				String delimiter = "";
 				for (Expression e: children) {
-					exp += (delimiter + e.toImplementation());
+					exp += (delimiter + e.toImplementation(sideEffects));
 					delimiter = ",";
 				}
 				return exp + ")";
@@ -265,7 +307,7 @@
 				String delimiter = "";
 				for (int i = 0; i < children.size(); i++) {
 					Expression e = children.get(implParamOrder[i]);
-					exp += (delimiter + e.toImplementation());
+					exp += (delimiter + e.toImplementation(sideEffects));
 					delimiter = ",";
 				}
 				return exp + ")";
diff --git a/AlgebraicDataflowArchitectureModel/src/models/dataConstraintModel/DataConstraintModel.java b/AlgebraicDataflowArchitectureModel/src/models/dataConstraintModel/DataConstraintModel.java
index 7599d14..39d644b 100644
--- a/AlgebraicDataflowArchitectureModel/src/models/dataConstraintModel/DataConstraintModel.java
+++ b/AlgebraicDataflowArchitectureModel/src/models/dataConstraintModel/DataConstraintModel.java
@@ -37,13 +37,26 @@
 	public static final Symbol cons = new Symbol("cons", 2, Symbol.Type.PREFIX, "add", Symbol.Type.METHOD_WITH_SIDE_EFFECT, new int[] {1, 0});
 	public static final Symbol head = new Symbol("head", 1, Symbol.Type.PREFIX, "($x)->$x.get(0)", Symbol.Type.LAMBDA);
 	public static final Symbol tail = new Symbol("tail", 1, Symbol.Type.PREFIX, "($x)->$x.subList(1, $x.size())", Symbol.Type.LAMBDA);
+	public static final Symbol get = new Symbol("get", 2, Symbol.Type.PREFIX, "get", Symbol.Type.METHOD);
+	public static final Symbol set = new Symbol("set", 3, Symbol.Type.PREFIX, "set", Symbol.Type.METHOD_WITH_SIDE_EFFECT);
 	public static final Symbol contains = new Symbol("contains", 2, Symbol.Type.PREFIX, "contains", Symbol.Type.METHOD);
+	public static final Symbol nil = new Symbol("nil", 0, Symbol.Type.PREFIX, "new ArrayList<>()", Symbol.Type.PREFIX);
 	public static final Symbol cond = new Symbol("if", 3, Symbol.Type.PREFIX, "($x,$y,$z)->($x ? $y : $z)", Symbol.Type.LAMBDA);
 	public static final Symbol eq = new Symbol("eq", 2, Symbol.Type.PREFIX, "==", Symbol.Type.INFIX);
 	public static final Symbol neq = new Symbol("neq", 2, Symbol.Type.PREFIX, "!=", Symbol.Type.INFIX);
 	public static final Symbol gt = new Symbol("gt", 2, Symbol.Type.PREFIX, ">", Symbol.Type.INFIX);
 	public static final Symbol lt = new Symbol("lt", 2, Symbol.Type.PREFIX, "<", Symbol.Type.INFIX);
-	public static final Symbol tuple = new Symbol("tuple", -1, Symbol.Type.PREFIX, "new AbstractMap.SimpleEntry<>", Symbol.Type.PREFIX);
+	public static final Symbol tuple = new Symbol("tuple", -1, Symbol.Type.PREFIX, new Symbol.IImplGenerator() {
+		@Override
+		public String generate(Type type, String[] childrenImpl, String[] sideEffects) {
+			String impl = "new AbstractMap.SimpleEntry<>(" + childrenImpl[0] + "$x)";
+			for (int i = 1; i < childrenImpl.length - 1; i++) {
+				impl = impl.replace("$x", ", new AbstractMap.SimpleEntry<>(" + childrenImpl[i] + "$x)");
+			}
+			impl = impl.replace("$x", ", " + childrenImpl[childrenImpl.length - 1]);
+			return impl;
+		}
+	});
 	public static final Symbol fst = new Symbol("fst", 1, Symbol.Type.PREFIX, "getKey", Symbol.Type.METHOD);
 	public static final Symbol snd = new Symbol("snd", 1, Symbol.Type.PREFIX, "getValue", Symbol.Type.METHOD);
 		
@@ -56,6 +69,8 @@
 		cons.setInverses(new Symbol[] {head, tail});
 		cons.setSignature(new Type[] {typeList, null, typeList});
 		contains.setSignature(new Type[] {typeBoolean, typeList, null});
+		get.setSignature(new Type[] {null, typeList, typeInt});
+		set.setSignature(new Type[] {typeList, typeList, typeInt, null});
 		tuple.setSignature(new Type[] {typeTuple, null, null});
 		tuple.setInverses(new Symbol[] {fst, snd});
 		fst.setSignature(new Type[] {null, typeTuple});
@@ -85,6 +100,9 @@
 		addSymbol(head);
 		addSymbol(tail);
 		addSymbol(contains);
+		addSymbol(get);
+		addSymbol(set);
+		addSymbol(nil);
 		addSymbol(cond);
 		addSymbol(eq);
 		addSymbol(neq);
diff --git a/AlgebraicDataflowArchitectureModel/src/parser/Parser.java b/AlgebraicDataflowArchitectureModel/src/parser/Parser.java
index d8307eb..500d428 100644
--- a/AlgebraicDataflowArchitectureModel/src/parser/Parser.java
+++ b/AlgebraicDataflowArchitectureModel/src/parser/Parser.java
@@ -205,8 +205,13 @@
 				} else {
 					// constant or variable
 					try {
-						Double d = Double.parseDouble(symbolName);
-						exp = new Constant(symbolName);
+						Symbol symbol = model.getSymbol(symbolName);
+						if (symbol != null && symbol.getArity() == 0) {
+							exp = new Constant(symbol);
+						} else {
+							Double d = Double.parseDouble(symbolName);
+							exp = new Constant(symbolName);
+						}
 					} catch (NumberFormatException e) {
 						if (stream.checkNext() != null && stream.checkNext().equals(COLON)) {
 							// when a type is specified.
diff --git a/AlgebraicDataflowArchitectureModel/src/tests/ParseTest.java b/AlgebraicDataflowArchitectureModel/src/tests/ParseTest.java
index 04ad162..56d3740 100644
--- a/AlgebraicDataflowArchitectureModel/src/tests/ParseTest.java
+++ b/AlgebraicDataflowArchitectureModel/src/tests/ParseTest.java
@@ -38,7 +38,8 @@
 				
 				for (ChannelGenerator c: model.getChannelGenerators()) {
 					for (ChannelMember out: ((DataflowChannelGenerator) c).getOutputChannelMembers()) {
-						System.out.println("next" + out.getIdentifierTemplate().getResourceName() + " = " + ((DataflowChannelGenerator) c).deriveUpdateExpressionOf(out).toImplementation());
+						String[] sideEffects = new String[] {""};
+						System.out.println("next" + out.getIdentifierTemplate().getResourceName() + " = " + ((DataflowChannelGenerator) c).deriveUpdateExpressionOf(out).toImplementation(sideEffects));
 					}
 				}
 				
diff --git a/AlgebraicDataflowArchitectureModel/src/tests/UpdateCodeGenerationTest.java b/AlgebraicDataflowArchitectureModel/src/tests/UpdateCodeGenerationTest.java
index 870769f..7d9d901 100644
--- a/AlgebraicDataflowArchitectureModel/src/tests/UpdateCodeGenerationTest.java
+++ b/AlgebraicDataflowArchitectureModel/src/tests/UpdateCodeGenerationTest.java
@@ -142,8 +142,9 @@
 		System.out.println(c1);
 		
 		try {
+			String[] sideEffects = new String[] {""};
 			System.out.println("-----");			
-			System.out.println(c1.deriveUpdateExpressionOf(c1_loyalty).toImplementation());
+			System.out.println(c1.deriveUpdateExpressionOf(c1_loyalty).toImplementation(sideEffects));
 			
 			System.out.println("-- PUSH --");
 			Expression loyaltyPushUpdate = c1.deriveUpdateExpressionOf(c1_loyalty, pushAccessor);
@@ -154,13 +155,13 @@
 					break;
 				}
 			}
-			System.out.println("void update(" + param.getType().getImplementationTypeName() + " " + param.toImplementation() + ") {");
-			System.out.println("\t" + fLoyalty + " = " + loyaltyPushUpdate.toImplementation() + ";");
+			System.out.println("void update(" + param.getType().getImplementationTypeName() + " " + param.toImplementation(sideEffects) + ") {");
+			System.out.println("\t" + fLoyalty + " = " + loyaltyPushUpdate.toImplementation(sideEffects) + ";");
 			System.out.println("}");
 			
 			System.out.println("-- PULL --");
 			System.out.println(loyalty.getResourceStateType().getImplementationTypeName() + " " + loyltyGetter.toImplementation() + "() {");
-			System.out.println("\t return " + c1.deriveUpdateExpressionOf(c1_loyalty, pullAccessor).toImplementation() + ";");
+			System.out.println("\t return " + c1.deriveUpdateExpressionOf(c1_loyalty, pullAccessor).toImplementation(sideEffects) + ";");
 			System.out.println("}");
 		} catch (ParameterizedIdentifierIsFutureWork | ResolvingMultipleDefinitionIsFutureWork | InvalidMessage
 				| UnificationFailed | ValueUndefined e) {
@@ -204,8 +205,9 @@
 		System.out.println(c2);		
 		
 		try {
+			String[] sideEffects = new String[] {""};
 			System.out.println("-----");
-			System.out.println(c2.deriveUpdateExpressionOf(c2_history).toImplementation());
+			System.out.println(c2.deriveUpdateExpressionOf(c2_history).toImplementation(sideEffects));
 			
 			System.out.println("-- PUSH --");
 			Expression historyPushUpdate = c2.deriveUpdateExpressionOf(c2_history, pushAccessor);
@@ -216,13 +218,13 @@
 					break;
 				}
 			}
-			System.out.println("void update(" + param.getType().getImplementationTypeName() + " " + param.toImplementation() + ") {");
-			System.out.println("\t" + fHistory + " = " + historyPushUpdate.toImplementation() + ";");
+			System.out.println("void update(" + param.getType().getImplementationTypeName() + " " + param.toImplementation(sideEffects) + ") {");
+			System.out.println("\t" + fHistory + " = " + historyPushUpdate.toImplementation(sideEffects) + ";");
 			System.out.println("}");
 			
 			System.out.println("-- PULL --");
 			System.out.println(history.getResourceStateType().getImplementationTypeName() + " " + historyGetter.toImplementation() + "() {");
-			System.out.println("\t return " + c2.deriveUpdateExpressionOf(c2_history, pullAccessor).toImplementation() + ";");
+			System.out.println("\t return " + c2.deriveUpdateExpressionOf(c2_history, pullAccessor).toImplementation(sideEffects) + ";");
 			System.out.println("}");
 		} catch (ParameterizedIdentifierIsFutureWork | ResolvingMultipleDefinitionIsFutureWork | InvalidMessage
 				| UnificationFailed | ValueUndefined e) {
@@ -266,8 +268,9 @@
 		System.out.println(c3);
 
 		try {
+			String[] sideEffects = new String[] {""};
 			System.out.println("-----");
-			System.out.println(c3.deriveUpdateExpressionOf(c3_total).toImplementation());
+			System.out.println(c3.deriveUpdateExpressionOf(c3_total).toImplementation(sideEffects));
 			
 			System.out.println("-- PUSH --");
 			Expression totalPushUpdate = c3.deriveUpdateExpressionOf(c3_total, pushAccessor);
@@ -278,13 +281,13 @@
 					break;
 				}
 			}
-			System.out.println("void update(" + param.getType().getImplementationTypeName() + " " + param.toImplementation() + ") {");
-			System.out.println("\t" + fTotal + " = " + totalPushUpdate.toImplementation() + ";");
+			System.out.println("void update(" + param.getType().getImplementationTypeName() + " " + param.toImplementation(sideEffects) + ") {");
+			System.out.println("\t" + fTotal + " = " + totalPushUpdate.toImplementation(sideEffects) + ";");
 			System.out.println("}");
 			
 			System.out.println("-- PULL --");
 			System.out.println(total.getResourceStateType().getImplementationTypeName() + " " + totalGetter.toImplementation() + "() {");
-			System.out.println("\t return " + c3.deriveUpdateExpressionOf(c3_total, pullAccessor).toImplementation() + ";");
+			System.out.println("\t return " + c3.deriveUpdateExpressionOf(c3_total, pullAccessor).toImplementation(sideEffects) + ";");
 			System.out.println("}");
 		} catch (ParameterizedIdentifierIsFutureWork | ResolvingMultipleDefinitionIsFutureWork | InvalidMessage
 				| UnificationFailed | ValueUndefined e) {