catch timeout and report it to prolog

src/main/java/de/stups/probkodkod/Request.java

@@ -63,6 +63,7 @@ public final class Request {
 	 *         have been send to the stream
 	 */
 	public boolean writeNextSolutions(final IPrologTermOutput pto, final int max) {
+		try {
 			boolean solutionsPresent = true;
 			int num;
 			int size = 0;
@@ -93,10 +94,18 @@ public final class Request {
 			pto.closeTerm();
 			pto.fullstop();
 			if (logger.isLoggable(Level.FINE)) {
-			logger.fine("wrote " + num + " solutions, computed in " + duration
-					+ "ms");
+				logger.fine("wrote " + num + " solutions, computed in "
+						+ duration + "ms");
 			}
 			return solutionsPresent;
+		} catch (RuntimeException ex) {
+			// timeout of the solver is wrapped in a runtime exception
+			if ("timed out".equals(ex.getMessage())) {
+				pto.printAtom("sat_timeout");
+				return true;
+			}
+			throw (ex);
+		}
 	}
 
 	private void printInstances(Instance[] solutions, IPrologTermOutput pto) {