diff --git a/prism/src/explicit/AccumulationContext.java b/prism/src/explicit/AccumulationContext.java
index e4d1e9b6..0d597180 100644
--- a/prism/src/explicit/AccumulationContext.java
+++ b/prism/src/explicit/AccumulationContext.java
@@ -2,7 +2,6 @@ package explicit;
 
 import java.util.HashMap;
 import java.util.Map;
-import java.util.Vector;
 
 import explicit.rewards.MCRewards;
 import explicit.rewards.MDPRewards;
diff --git a/prism/src/explicit/AccumulationProduct.java b/prism/src/explicit/AccumulationProduct.java
index 2cbdb812..dbcc595e 100644
--- a/prism/src/explicit/AccumulationProduct.java
+++ b/prism/src/explicit/AccumulationProduct.java
@@ -5,10 +5,7 @@ import java.util.BitSet;
 import java.util.HashMap;
 import java.util.Iterator;
 import java.util.Map;
-import java.util.Vector;
 
-import parser.ast.AccumulationTerm;
-import prism.IntegerBound;
 import prism.PrismException;
 
 import common.Dottable;
diff --git a/prism/src/explicit/AccumulationProductCounting.java b/prism/src/explicit/AccumulationProductCounting.java
index ee4c8e03..320619f4 100644
--- a/prism/src/explicit/AccumulationProductCounting.java
+++ b/prism/src/explicit/AccumulationProductCounting.java
@@ -2,7 +2,6 @@ package explicit;
 
 import java.util.BitSet;
 import java.util.HashMap;
-import java.util.Vector;
 
 import explicit.rewards.Rewards;
 import prism.IntegerBound;
diff --git a/prism/src/explicit/AccumulationProductRegular.java b/prism/src/explicit/AccumulationProductRegular.java
index ed7d7893..678e874e 100644
--- a/prism/src/explicit/AccumulationProductRegular.java
+++ b/prism/src/explicit/AccumulationProductRegular.java
@@ -3,7 +3,6 @@ package explicit;
 import java.util.ArrayList;
 import java.util.BitSet;
 import java.util.HashMap;
-import java.util.Vector;
 
 import automata.finite.DeterministicFiniteAutomaton;
 import automata.finite.EdgeLabel;
diff --git a/prism/src/explicit/AccumulationTrack.java b/prism/src/explicit/AccumulationTrack.java
index 13fd6b62..1eec57d8 100644
--- a/prism/src/explicit/AccumulationTrack.java
+++ b/prism/src/explicit/AccumulationTrack.java
@@ -1,9 +1,6 @@
 package explicit;
 
 import java.util.HashMap;
-import java.util.Vector;
-
-import explicit.rewards.Rewards;
 
 /**
  * An AccumulationTrack contains a map of weights
diff --git a/prism/src/explicit/AccumulationTransformation.java b/prism/src/explicit/AccumulationTransformation.java
index 31e392f5..a7e172b4 100644
--- a/prism/src/explicit/AccumulationTransformation.java
+++ b/prism/src/explicit/AccumulationTransformation.java
@@ -3,7 +3,6 @@ package explicit;
 import java.util.ArrayList;
 import java.util.BitSet;
 import java.util.HashMap;
-import java.util.Vector;
 
 import common.StopWatch;
 import explicit.rewards.ConstructRewards;
diff --git a/prism/src/parser/ast/ExpressionAccumulationConstraint.java b/prism/src/parser/ast/ExpressionAccumulationConstraint.java
index 754f8ba1..0d74f056 100644
--- a/prism/src/parser/ast/ExpressionAccumulationConstraint.java
+++ b/prism/src/parser/ast/ExpressionAccumulationConstraint.java
@@ -149,15 +149,15 @@ public class ExpressionAccumulationConstraint extends Expression
 	{
 		switch (op) {
 		case BASIC:
-			return new Boolean(operand1.evaluateBoolean(ec));
+			return operand1.evaluateBoolean(ec);
 		case IMPLIES:
-			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 NOT:
-			return new Boolean(!operand1.evaluateBoolean(ec));
+			return !operand1.evaluateBoolean(ec);
 		}
 		throw new PrismLangException("Unknown accumulation constraint operator", this);
 	}
@@ -202,7 +202,11 @@ public class ExpressionAccumulationConstraint extends Expression
 	@Override
 	public String toString()
 	{
-		return operand1 + opSymbols[op] + operand2;
+		String op1;
+		String op2;
+		if(operand1.op != BASIC) { op1 = "(" + operand1 + ")"; } else { op1 = operand1.toString(); }
+		if(operand2.op != BASIC) { op2 = "(" + operand2 + ")"; } else { op2 = operand2.toString(); }
+		return op1 + " " + opSymbols[op] + " " + op2;
 	}
 
 	@Override
diff --git a/prism/src/parser/visitor/EvaluateAccumulationConstraints.java b/prism/src/parser/visitor/EvaluateAccumulationConstraints.java
index 50f3a2d0..441d487e 100644
--- a/prism/src/parser/visitor/EvaluateAccumulationConstraints.java
+++ b/prism/src/parser/visitor/EvaluateAccumulationConstraints.java
@@ -1,5 +1,10 @@
 package parser.visitor;
 
-public class EvaluateAccumulationConstraints extends ASTTraverseModify {
+import explicit.AccumulationTrack;
+import parser.ast.AccumulationTerm;
+import prism.IntegerBound;
+import prism.PrismException;
 
+public class EvaluateAccumulationConstraints<Component> extends ASTTraverseModify {
+	
 }