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SPL(Structured Process Language) A programming language specially for structured data computing.

There is a newer version: 20240823

package com.scudata.expression;

import com.scudata.dm.ComputeStack;
import com.scudata.dm.Context;
import com.scudata.dm.Current;
import com.scudata.dm.Sequence;

/**
 * ????????Ļ??ܺ????̳д???
 * @author RunQian
 *
 */
abstract public class Gather extends Function {
	/**
	 * ?Խڵ????Ż???????????ʽ????ɳ???
	 * @param ctx ??????????
	 * @param Node ?Ż???Ľڵ?
	 */
	public Node optimize(Context ctx) {
		if (param != null) {
			param.optimize(ctx);
		}
		
		return this;
	}

	/**
	 * ??????????ǰ׼??????
	 * @param ctx ??????????
	 */
	abstract public void prepare(Context ctx);

	/**
	 * ??????????????¼?Ļ???ֵ
	 * @param ctx ??????????
	 * @return ????ֵ
	 */
	abstract public Object gather(Context ctx);

	/**
	 * ???㵱ǰ??¼??ֵ?????ܵ?֮ǰ?Ļ??ܽ??oldValue??
	 * @param oldValue ֮ǰ?Ļ??ܽ??
	 * @param ctx ??????????
	 * @return ????ֵ
	 */
	abstract public Object gather(Object oldValue, Context ctx);
	
	/**
	 * ȡ???λ??ܶ?Ӧ?ı???ʽ
	 * ???̷߳???ʱ??ÿ???߳????һ???????????????Ҫ?ڵ?һ?η??????????????η???
	 * @param q ?????ֶ????
	 * @return Expression
	 */
	abstract public Expression getRegatherExpression(int q);
	
	/**
	 * ??һ?????????ʱ?Ƿ???Ҫ????finish1?Ի???ֵ?????״δ?????top??Ҫ????
	 * @return true????Ҫ??false??????Ҫ
	 */
	//public boolean needFinish1() {
	//	return false;
	//}
	
	/**
	 * ?Ե?һ?η???õ??Ļ???ֵ?????״δ????????????ֵ??Ҫ?μӶ??η???????
	 * @param val ????ֵ
	 * @return ??????Ļ???ֵ
	 */
	//public Object finish1(Object val) {
	//	return val;
	//}
	
	/**
	 * ?Ƿ???Ҫ?????ջ???ֵ???д???
	 * @return true????Ҫ??false??????Ҫ
	 */
	//public boolean needFinish() {
	//	return false;
	//}
	
	/**
	 * ?Է???????õ??Ļ???ֵ???????մ???????ƽ??ֵ??Ҫ??sum/count????
	 * @param val ????ֵ
	 * @return ??????Ļ???ֵ
	 */
	//public Object finish(Object val) {
	//	return val;
	//}
	
	/**
	 * ??Ը??????????????ֵ
	 * @param seq ????
	 * @param ctx ??????????
	 * @return ????ֵ
	 */
	public Object gather(Sequence seq, Context ctx) {
		if (seq == null || seq.length() == 0) {
			return null;
		}
		
		ComputeStack stack = ctx.getComputeStack();
		Current current = new Current(seq, 1);
		stack.push(current);

		try {
			Object result = gather(ctx);
			for (int i = 2, len = seq.length(); i <= len; ++i) {
				current.setCurrent(i);
				result = gather(result, ctx);
			}
			
			return finish(result);
		} finally {
			stack.pop();
		}
	}
}