class StringConsumerEngine inherits System {
	consumers: ConsumerList <- (new ConsumerList)
		.push((new WhitespaceConsumer).init())
		.push((new ExpressionConsumer).init())
		.push((new IfConsumer).init())
		;

	str: String;
	tl: TokenList <- new TokenList;

	init(code: String) : Object {{
		assert(not (code = ""), "init", "input code cannot be empty!");
		assert(str = "", "init", "already initialised!");

		str <- code;
	}};

	try_consume() : Bool {
		let
			consumer: Object <- consumers.find(str)
		in
			if isvoid consumer
			then
				false
			else
				case consumers.find(str) of
					c: IStringConsumer => {
						str <- str.substr(c.consumed_length(), str.length() - c.consumed_length());
						tl.push(c.token());
						true;
					};
					o: Object => false;
				esac
			fi
	};

	out() : Object {
		out_string(str)
	};

	empty() : Bool {
		str = ""
	};

	generated_tokens() : TokenList {
		tl
	};
};