public PreviousMovesExtractor(GameState prevPrevSource, ArimaaMove prevPrevMove, GameState prevSource, ArimaaMove prevMove, GameState currSource,  ArimaaMove currMove) {
		
		GenTurn turnGenerator = new GenTurn();
		if(prevPrevSource!=null && prevPrevMove!=null) {
			String prevPrevMoveStr = turnGenerator.getOfficialArimaaNotation(prevPrevSource, prevPrevMove);
			prevPrevStepSources = Utilities.getStepSources(prevPrevMoveStr);
		}
		if(prevSource!=null && prevMove!=null) {
			String prevMoveStr = turnGenerator.getOfficialArimaaNotation(prevSource, prevMove);
			prevStepSources = Utilities.getStepSources(prevMoveStr);
		}
		if(currSource!=null && currMove!=null) {
			String currMoveStr = turnGenerator.getOfficialArimaaNotation(currSource, currMove);
			currStepSources = Utilities.getStepSources(currMoveStr);
		}
		featureVector = null;
	}