plus.java

symbman（大学作业）

import java.util.Vector;

public class Plus extends Expression {
	
	private Expression[] addends;
	
	public Plus(Expression[] a) {
		addends = new Expression[a.length];
		for(int i=0;i<a.length;i++)
			addends[i] = (Expression)a[i].clone();
	}
	
	public Expression[] getAddends() { return addends; }
	
	public Object clone() {
		return new Plus(addends);
	}

	public Expression eval() {
		Expression[] result = new Expression[addends.length];
		for(int i=0;i<addends.length;i++)
			result[i] = addends[i].eval();
		return new Plus(result);
	}

	public String toString() {
		StringBuffer result = new StringBuffer("(");
		result.append(addends[0].toString());
		for(int i=1;i<addends.length;i++) {
			result.append("+");
			result.append(addends[i].toString());
		}
		result.append(")");
			
		return result.toString();
	}
	
	public Expression derive(Symbol s) {
		Expression[] result = new Expression[addends.length];
		for(int i=0;i<addends.length;i++)
			result[i] = addends[i].derive(s);

		return new Plus(result);
	}
	
	public boolean equals(Expression ex) {
		if(!(ex instanceof Plus)) return false;
		Plus p = (Plus)ex;
		Expression eadd[] = p.getAddends();
		if(eadd.length == addends.length) {
			boolean ret = true;
			for(int i=0;i<addends.length;i++)
				if(!(eadd[i].equals(addends[i]))) {
					ret = false;
					//break;
				}
			return ret;
		}
		else return false;
	}
	
	public Expression simplify() {
		Vector v = new Vector();
		for(int i=0;i<addends.length;i++) {
			if(!((addends[i].simplify()).equals(new NumericValue(0.0))))
				v.add(addends[i].simplify());
		}
			
		Expression simplAddends[] = new Expression[v.size()];
		for(int i=0;i<v.size();i++)
			simplAddends[i] = (Expression) v.get(i);
		
		return new Plus(simplAddends);
			
	}

}