Get "java.util.NoSuchElementException" while reasoning

[galigator]

Get "java.util.NoSuchElementException" while reasoning

[greeny277]

I'm using version 2.6.4-SNAPSHOT. However, the Pellet reasoner already has this bug.

[ignazio1977]

at least use a try{...}catch(Exception e){...} construct

That's a reasonable expectation but the issue here is more subtle.

There is a .next() on an empty iterator, and from the code I suspect there is an incorrect condition being checked:

                 if (dtReasoner.isSatisfiable(types))
			{
				if (!dtReasoner.containsAtLeast(2, types))

                                   ^^^^^^^^^^^^^^^ This is strange. 

I think the ! is misplaced - it's trying to merge nodes when there are not at least two nodes, i.e., when there is one node or no nodes, like in this case. I suspect the intention was to only merge nodes when there are two or more nodes (and where the .next() operation would have been safe)

				{
					/*
					 * This literal is a variable, but given _current ranges can only
					 * take on a single _value.  Merge with that _value.
					 */
					final Object value = dtReasoner.valueIterator(types).next();
					final ATermAppl valueTerm = dtReasoner.getLiteral(value);
					Literal valueLiteral = _abox.getLiteral(valueTerm);
					if (valueLiteral == null)
						/*
						 * No dependency set is used here because omitting it prevents the
						 * constant literal from being removed during backtrack
						 */
						valueLiteral = _abox.addLiteral(valueTerm);
					DependencySet mergeDs = DependencySet.INDEPENDENT;
					for (final DependencySet ds : _depends.values())
						mergeDs = mergeDs.union(ds, _abox.doExplanation());
					_merge = new NodeMerge(this, valueLiteral, mergeDs);
				}
			}

[greeny277]

Ah ok. So I guess it's a bug that can be easily fixed.

[Galigator]

In fact I spend some weekends on it. It is harder to fix because simple change around this create problems elsewhere. It may need a modern rewrite with less mutable structures.