accumulation: small refactor

prism/src/explicit/ProbModelChecker.java

@@ -604,6 +604,9 @@ public class ProbModelChecker extends NonProbModelChecker
 
 	protected StateValues checkProbPathFormulaAccumulationExpression(Model model, Expression expr, MinMax minMax, BitSet statesOfInterest) throws PrismException
 	{
+		if (!(model.getModelType() == ModelType.DTMC || model.getModelType() == ModelType.MDP)) {
+			throw new PrismException("Model checking of accumulation expressions formulas is not supported for "+model.getModelType().name());
+		}
 		// Do a transformation and a projection
 		AccumulationTransformation<?> accTrans = new AccumulationTransformation<ModelExplicit>(this, (ModelExplicit)model, expr, statesOfInterest);
 		StateValues transValues = this.checkProbPathFormula(accTrans.getTransformedModel(), accTrans.getTransformedExpression(), minMax, accTrans.getTransformedStatesOfInterest());
@@ -636,11 +639,7 @@ public class ProbModelChecker extends NonProbModelChecker
 		if (useSimplePathAlgo) {
 			return checkProbPathFormulaSimple(model, expr, minMax, statesOfInterest);
 		} else if (Expression.containsAccumulationExpression(expr)) {
-			if (model.getModelType() == ModelType.DTMC || model.getModelType() == ModelType.MDP) {
-				return this.checkProbPathFormulaAccumulationExpression(model, expr, minMax, statesOfInterest);
-			} else {
-				throw new PrismException("Model checking of accumulation expressions formulas is not supported for "+model.getModelType().name());
-			}
+			return this.checkProbPathFormulaAccumulationExpression(model, expr, minMax, statesOfInterest);
 		} else {	
 			return checkProbPathFormulaLTL(model, expr, false, minMax, statesOfInterest);
 		}