Better isDFA() check for DRAs.

git-svn-id: https://www.prismmodelchecker.org/svn/prism/prism/trunk@9434 bbc10eb1-c90d-0410-af57-cb519fbb1720

prism/src/prism/DRA.java

@@ -212,19 +212,22 @@ public class DRA<Symbol>
 	
 	/**
 	 * Is this Rabin automaton actually a finite automaton? This check is done syntactically:
-	 * it returns true if L_i is empty for any acceptance pairs (L_i,K_i)
-	 * and every transition from a K_i state goes to another K_i state.
+	 * it returns true if every transition from a K_i state goes to another K_i state.
+	 * We also require that there are no L_i states overlapping with any K_j states. 
 	 */
 	public boolean isDFA()
 	{
-		if (!isDBA())
-			return false;
 		// Compute union of all K_i sets
 		BitSet acc = new BitSet();
 		int n = getNumAcceptancePairs();
 		for (int i = 0; i < n; i++) {
 			acc.or(getAcceptanceK(i));
 		}
+		// Make sure there are no L_i states in any K_j states
+		for (int i = 0; i < n; i++) {
+			if (acc.intersects(getAcceptanceL(i)))
+				return false;
+		}
 		// Check if every transition from a K_i state goes to another K_i state.
 		for (int i = acc.nextSetBit(0); i >= 0; i = acc.nextSetBit(i + 1)) {
 			int m = getNumEdges(i);