diff --git a/prism/src/parser/ast/ExpressionBinaryOp.java b/prism/src/parser/ast/ExpressionBinaryOp.java
index 9e78cf62..27131c13 100644
--- a/prism/src/parser/ast/ExpressionBinaryOp.java
+++ b/prism/src/parser/ast/ExpressionBinaryOp.java
@@ -147,69 +147,69 @@ public class ExpressionBinaryOp extends Expression
 	{
 		switch (op) {
 		case IMPLIES:
-			return new Boolean(!operand1.evaluateBoolean(ec) || operand2.evaluateBoolean(ec));
+			return !operand1.evaluateBoolean(ec) || operand2.evaluateBoolean(ec);
 		case IFF:
-			return new Boolean(operand1.evaluateBoolean(ec) == operand2.evaluateBoolean(ec));
+			return operand1.evaluateBoolean(ec) == operand2.evaluateBoolean(ec);
 		case OR:
-			return new Boolean(operand1.evaluateBoolean(ec) || operand2.evaluateBoolean(ec));
+			return operand1.evaluateBoolean(ec) || operand2.evaluateBoolean(ec);
 		case AND:
-			return new Boolean(operand1.evaluateBoolean(ec) && operand2.evaluateBoolean(ec));
+			return operand1.evaluateBoolean(ec) && operand2.evaluateBoolean(ec);
 		case EQ:
 			if (operand1.getType() == TypeInt.getInstance() && operand2.getType() == TypeInt.getInstance()) {
-				return new Boolean(operand1.evaluateInt(ec) == operand2.evaluateInt(ec));
+				return operand1.evaluateInt(ec) == operand2.evaluateInt(ec);
 			} else {
-				return new Boolean(operand1.evaluateDouble(ec) == operand2.evaluateDouble(ec));
+				return operand1.evaluateDouble(ec) == operand2.evaluateDouble(ec);
 			}
 		case NE:
 			if (operand1.getType() == TypeInt.getInstance() && operand2.getType() == TypeInt.getInstance()) {
-				return new Boolean(operand1.evaluateInt(ec) != operand2.evaluateInt(ec));
+				return operand1.evaluateInt(ec) != operand2.evaluateInt(ec);
 			} else {
-				return new Boolean(operand1.evaluateDouble(ec) != operand2.evaluateDouble(ec));
+				return operand1.evaluateDouble(ec) != operand2.evaluateDouble(ec);
 			}
 		case GT:
 			if (operand1.getType() == TypeInt.getInstance() && operand2.getType() == TypeInt.getInstance()) {
-				return new Boolean(operand1.evaluateInt(ec) > operand2.evaluateInt(ec));
+				return operand1.evaluateInt(ec) > operand2.evaluateInt(ec);
 			} else {
-				return new Boolean(operand1.evaluateDouble(ec) > operand2.evaluateDouble(ec));
+				return operand1.evaluateDouble(ec) > operand2.evaluateDouble(ec);
 			}
 		case GE:
 			if (operand1.getType() == TypeInt.getInstance() && operand2.getType() == TypeInt.getInstance()) {
-				return new Boolean(operand1.evaluateInt(ec) >= operand2.evaluateInt(ec));
+				return operand1.evaluateInt(ec) >= operand2.evaluateInt(ec);
 			} else {
-				return new Boolean(operand1.evaluateDouble(ec) >= operand2.evaluateDouble(ec));
+				return operand1.evaluateDouble(ec) >= operand2.evaluateDouble(ec);
 			}
 		case LT:
 			if (operand1.getType() == TypeInt.getInstance() && operand2.getType() == TypeInt.getInstance()) {
-				return new Boolean(operand1.evaluateInt(ec) < operand2.evaluateInt(ec));
+				return operand1.evaluateInt(ec) < operand2.evaluateInt(ec);
 			} else {
-				return new Boolean(operand1.evaluateDouble(ec) < operand2.evaluateDouble(ec));
+				return operand1.evaluateDouble(ec) < operand2.evaluateDouble(ec);
 			}
 		case LE:
 			if (operand1.getType() == TypeInt.getInstance() && operand2.getType() == TypeInt.getInstance()) {
-				return new Boolean(operand1.evaluateInt(ec) <= operand2.evaluateInt(ec));
+				return operand1.evaluateInt(ec) <= operand2.evaluateInt(ec);
 			} else {
-				return new Boolean(operand1.evaluateDouble(ec) <= operand2.evaluateDouble(ec));
+				return operand1.evaluateDouble(ec) <= operand2.evaluateDouble(ec);
 			}
 		case PLUS:
 			if (operand1.getType() == TypeInt.getInstance() && operand2.getType() == TypeInt.getInstance()) {
-				return new Integer(operand1.evaluateInt(ec) + operand2.evaluateInt(ec));
+				return operand1.evaluateInt(ec) + operand2.evaluateInt(ec);
 			} else {
-				return new Double(operand1.evaluateDouble(ec) + operand2.evaluateDouble(ec));
+				return operand1.evaluateDouble(ec) + operand2.evaluateDouble(ec);
 			}
 		case MINUS:
 			if (operand1.getType() == TypeInt.getInstance() && operand2.getType() == TypeInt.getInstance()) {
-				return new Integer(operand1.evaluateInt(ec) - operand2.evaluateInt(ec));
+				return operand1.evaluateInt(ec) - operand2.evaluateInt(ec);
 			} else {
-				return new Double(operand1.evaluateDouble(ec) - operand2.evaluateDouble(ec));
+				return operand1.evaluateDouble(ec) - operand2.evaluateDouble(ec);
 			}
 		case TIMES:
 			if (operand1.getType() == TypeInt.getInstance() && operand2.getType() == TypeInt.getInstance()) {
-				return new Integer(operand1.evaluateInt(ec) * operand2.evaluateInt(ec));
+				return operand1.evaluateInt(ec) * operand2.evaluateInt(ec);
 			} else {
-				return new Double(operand1.evaluateDouble(ec) * operand2.evaluateDouble(ec));
+				return operand1.evaluateDouble(ec) * operand2.evaluateDouble(ec);
 			}
 		case DIVIDE:
-			return new Double(operand1.evaluateDouble(ec) / operand2.evaluateDouble(ec));
+			return operand1.evaluateDouble(ec) / operand2.evaluateDouble(ec);
 		}
 		throw new PrismLangException("Unknown binary operator", this);
 	}
diff --git a/prism/src/parser/ast/ExpressionFunc.java b/prism/src/parser/ast/ExpressionFunc.java
index a8f3be7d..0fd96ef6 100644
--- a/prism/src/parser/ast/ExpressionFunc.java
+++ b/prism/src/parser/ast/ExpressionFunc.java
@@ -231,7 +231,7 @@ public class ExpressionFunc extends Expression
 				j = getOperand(i).evaluateInt(ec);
 				iMin = (j < iMin) ? j : iMin;
 			}
-			return new Integer(iMin);
+			return iMin;
 		} else {
 			dMin = getOperand(0).evaluateDouble(ec);
 			n = getNumOperands();
@@ -239,7 +239,7 @@ public class ExpressionFunc extends Expression
 				d = getOperand(i).evaluateDouble(ec);
 				dMin = (d < dMin) ? d : dMin;
 			}
-			return new Double(dMin);
+			return dMin;
 		}
 	}
 
@@ -266,7 +266,7 @@ public class ExpressionFunc extends Expression
 				j = getOperand(i).evaluateInt(ec);
 				iMax = (j > iMax) ? j : iMax;
 			}
-			return new Integer(iMax);
+			return iMax;
 		} else {
 			dMax = getOperand(0).evaluateDouble(ec);
 			n = getNumOperands();
@@ -274,7 +274,7 @@ public class ExpressionFunc extends Expression
 				d = getOperand(i).evaluateDouble(ec);
 				dMax = (d > dMax) ? d : dMax;
 			}
-			return new Double(dMax);
+			return dMax;
 		}
 	}
 
@@ -362,9 +362,9 @@ public class ExpressionFunc extends Expression
 	{
 		try {
 			if (type instanceof TypeInt) {
-				return new Integer(evaluatePowInt(getOperand(0).evaluateInt(ec), getOperand(1).evaluateInt(ec)));
+				return evaluatePowInt(getOperand(0).evaluateInt(ec), getOperand(1).evaluateInt(ec));
 			} else {
-				return new Double(evaluatePowDouble(getOperand(0).evaluateDouble(ec), getOperand(1).evaluateDouble(ec)));
+				return evaluatePowDouble(getOperand(0).evaluateDouble(ec), getOperand(1).evaluateDouble(ec));
 			}
 		} catch (PrismLangException e) {
 			e.setASTElement(this);
@@ -408,7 +408,7 @@ public class ExpressionFunc extends Expression
 	public Object evaluateMod(EvaluateContext ec) throws PrismLangException
 	{
 		try {
-			return new Integer(evaluateMod(getOperand(0).evaluateInt(ec), getOperand(1).evaluateInt(ec)));
+			return evaluateMod(getOperand(0).evaluateInt(ec), getOperand(1).evaluateInt(ec));
 		} catch (PrismLangException e) {
 			e.setASTElement(this);
 			throw e;
@@ -439,7 +439,7 @@ public class ExpressionFunc extends Expression
 	public Object evaluateLog(EvaluateContext ec) throws PrismLangException
 	{
 		try {
-			return new Double(evaluateLog(getOperand(0).evaluateDouble(ec), getOperand(1).evaluateDouble(ec)));
+			return evaluateLog(getOperand(0).evaluateDouble(ec), getOperand(1).evaluateDouble(ec));
 		} catch (PrismLangException e) {
 			e.setASTElement(this);
 			throw e;
diff --git a/prism/src/parser/ast/ExpressionUnaryOp.java b/prism/src/parser/ast/ExpressionUnaryOp.java
index 0c48975f..32fcb7d9 100644
--- a/prism/src/parser/ast/ExpressionUnaryOp.java
+++ b/prism/src/parser/ast/ExpressionUnaryOp.java
@@ -120,12 +120,12 @@ public class ExpressionUnaryOp extends Expression
 	{
 		switch (op) {
 		case NOT:
-			return new Boolean(!operand.evaluateBoolean(ec));
+			return !operand.evaluateBoolean(ec);
 		case MINUS:
 			if (type instanceof TypeInt) {
-				return new Integer(-operand.evaluateInt(ec));
+				return -operand.evaluateInt(ec);
 			} else {
-				return new Double(-operand.evaluateDouble(ec));
+				return -operand.evaluateDouble(ec);
 			}
 		case PARENTH:
 			return operand.evaluate(ec);