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

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package com.scudata.expression.fn.math;

import com.scudata.common.MessageManager;
import com.scudata.common.RQException;
import com.scudata.dm.Context;
import com.scudata.expression.Function;
import com.scudata.resources.EngineMessage;

/**
 * ????ĳһ???ֵķ?˫??????ֵacosh(z)=ln(z+sqrt(z*z-1))
 * @author yanjing
 *
 */
public class Arccosh extends Function {
	/**
	 * ??????ʽ????Ч?ԣ???Ч???׳??쳣
	 */
	public void checkValidity() {
		if (param == null) {
			MessageManager mm = EngineMessage.get();
			throw new RQException("acosh" + mm.getMessage("function.missingParam"));
		} else if (!param.isLeaf()) {
			MessageManager mm = EngineMessage.get();
			throw new RQException("acosh" + mm.getMessage("function.invalidParam"));
		}
	}

	public Object calculate(Context ctx) {
		Object obj = param.getLeafExpression().calculate(ctx);
		if (obj instanceof Number) {
			double z = ((Number)obj).doubleValue();
			return new Double(Math.log(z+Math.sqrt(z*z-1)));
		} else if (obj == null) {
			return null;
		} else {
			MessageManager mm = EngineMessage.get();
			throw new RQException("acosh" + mm.getMessage("function.paramTypeError"));
		}
	}
}