env.java

来自「用java实现的编译器. 包括语法分析」· Java 代码 · 共 23 行

package symbols;
import lexer.*;
import java.util.*;
import inter.*;
public class Env {
	public HashMap table;
	protected Env prev;
	public Env(Env n) { 
		table = new HashMap();
		prev = n;
	}
	@SuppressWarnings("unchecked")
	public void put(Token w, Id i) { table.put(w, i);}
	public Id get(Token w) {
		for(Env e = this; e != null; e = e.prev) {
			Id found = (Id)e.table.get(w);
			if(found != null)
				return found;
		}
		return null;
	}
}