sourceprinter.java

java语言开发的基于tiny语言的编译器

package jeex.tiny;

import java.io.*;
import java.util.*;
import jeex.tiny.Tree.*;

/**
 * Prints out a tiny source file.
 */
class SourcePrinter extends Tree.Visitor {
	PrintStream out = System.out;
	
	int indent = 0;
	
	SourcePrinter(PrintStream out) {
		this.out = out;
	}
	
	SourcePrinter() {
		this.out = System.out;
	}
	
	void _case(StmtSeq tree) {
		Vector v = tree.statements;
		for(int i = 0; i < v.size(); i++) {
			Tree tree1 = (Tree)v.get(i);
			tree1.visit(this);
			if (i == (v.size() - 1)) // the last statement
				out.println();
			else
				out.println(";");
		}
	}
	
	void _case(IfStmt tree) {
		indent();
		out.print("if ");
		tree.condition.visit(this);
		out.println(" then");
		indent ++; 
		tree.thenPart.visit(this);
		if (tree.elsePart != null) {
			indent --; indent();
			out.println("else");
			indent ++; 
			tree.elsePart.visit(this);
		}
		indent --; indent();
		out.print("end");
	}
	
	void _case(RepeatStmt tree) {
		indent();
		out.println("repeat");
		indent ++;
		tree.stmtSeq.visit(this);
		indent --;indent();
		out.print("until ");
		tree.condition.visit(this);
	}
	
	void _case(AssignStmt tree) {
		indent();
		out.print(tree.ident);
		out.print(" := ");
		tree.expr.visit(this);
	}
	
	void _case(ReadStmt tree) {
		indent();
		out.print("read ");
		out.print(tree.ident);
	}
	
	void _case(WriteStmt tree) {
		indent();
		out.print("write ");
		tree.expr.visit(this);
	}
	
	void _case(Expr tree) {
		tree.first.visit(this);
		if (tree.second != null) {
			out.print(tree.op == Tokens.LT ? " < " : " = ");
			tree.second.visit(this);		
		}		
	}
	
	void _case(ParExpr tree) {
		out.print("(");
		tree.expr.visit(this);
		out.print(")");
	}
	
	void _case(Operation tree) {
		tree.left.visit(this);
		out.print(" " + TokenUtil.tokenToString(tree.op) + " ");
		tree.right.visit(this);
	}
	
	void _case(Ident tree) {
		out.print(tree.name);
	}
	
	void _case(Literal tree) {
		out.print(tree.value);
	}

	void _case(ErrorTree tree) {
		out.print("ERROR");
	}
	
	private void indent() {
		for(int i = 0; i < indent; i++)
			out.print("    ");
	}
}