public Variable(int _name){
		//assign it's name
		name = _name;
		
		//it starts UNASSIGNED
		assignment = UNASSIGNED;
		
		//assume variables are choice
		value = -1.0;		
		
		timesPositive = 0;
		timesNegative = 0;
		//assumes it does not appear unit in any clauses.
		unitClauses = new Vector<Clause>();
	}