54 lines
1.5 KiB
Java
54 lines
1.5 KiB
Java
|
package com.craftinginterpreters.lox;
|
||
|
|
|
||
|
|
/**
|
||
|
|
* AstPrinter
|
||
|
|
*/
|
||
|
|
class AstPrinter implements Expr.Visitor<String> {
|
||
|
|
String print(Expr expr) {
|
||
|
|
return expr.accept(this);
|
||
|
|
}
|
||
|
|
|
||
|
|
@Override
|
||
|
|
public String visitBinaryExpr(Expr.Binary expr) {
|
||
|
|
return parenthesize(expr.operator.lexeme, expr.left, expr.right);
|
||
|
|
}
|
||
|
|
|
||
|
|
@Override
|
||
|
|
public String visitGroupingExpr(Expr.Grouping expr) {
|
||
|
|
return parenthesize("group", expr.expression);
|
||
|
|
}
|
||
|
|
|
||
|
|
@Override
|
||
|
|
public String visitLiteralExpr(Expr.Literal expr) {
|
||
|
|
if (expr.value == null)
|
||
|
|
return "nil";
|
||
|
|
return expr.value.toString();
|
||
|
|
}
|
||
|
|
|
||
|
|
@Override
|
||
|
|
public String visitUnaryExpr(Expr.Unary expr) {
|
||
|
|
return parenthesize(expr.operator.lexeme, expr.right);
|
||
|
|
}
|
||
|
|
|
||
|
|
private String parenthesize(String name, Expr... exprs) {
|
||
|
|
StringBuilder builder = new StringBuilder();
|
||
|
|
|
||
|
|
builder.append("(").append(name);
|
||
|
|
for (Expr expr : exprs) {
|
||
|
|
builder.append(" ");
|
||
|
|
builder.append(expr.accept(this));
|
||
|
|
}
|
||
|
|
builder.append(")");
|
||
|
|
|
||
|
|
return builder.toString();
|
||
|
|
}
|
||
|
|
|
||
|
|
public static void main(String[] args) {
|
||
|
|
Expr expression = new Expr.Binary(
|
||
|
|
new Expr.Unary(new Token(TokenType.MINUS, "-", null, 1), new Expr.Literal(123)),
|
||
|
|
new Token(TokenType.STAR, "*", null, 1), new Expr.Grouping(new Expr.Literal(45.67)));
|
||
|
|
|
||
|
|
System.out.println(new AstPrinter().print(expression));
|
||
|
|
}
|
||
|
|
}
|