private Tree variablePro(){
		Symbol identifier = null;
		Tree expression = null;
		
		if((identifier = accept(Symbol.Id.IDENTIFIER_NAME))!=null){
			if((accept(Symbol.Id.PUNCTUATORS,"="))!=null){
				if((expression = expressionPro())!=null){
					return new Variable(identifier, expression);
				}
				return null;
			}
			
			return new Variable(identifier);
		}
		
		return null;
	}