Initial commit

java/com/craftinginterpreters/lox/AstPrinter.java

@@ -0,0 +1,50 @@
+package com.craftinginterpreters.lox;
+
+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));
+  }
+}