[Chapter8&Fix] - Adding missing code and implemeting a little of the AstPrinter

src/com/lox/AstPrinter.java

@@ -5,6 +5,23 @@ class AstPrinter implements Expr.Visitor<String> {
     return expr.accept(this);
   }
   @Override
+  public String visitVariableExpr(Expr.Variable expr){
+    if(expr.name.literal == null){
+      return expr.name.lexeme;
+    }
+    return parenthesize(
+      "variable"
+      ,new Expr.Literal(expr.name.lexeme)
+      ,new Expr.Literal(expr.name.literal));
+  }
+
+  @Override
+  public String visitAssignExpr(Expr.Assign assign){
+    return parenthesize("set!"
+      ,new Expr.Literal(assign.name.lexeme)
+      ,assign.value);
+  }
+  @Override
   public String visitBinaryExpr(Expr.Binary expr) {
     return parenthesize(expr.operator.lexeme,
                         expr.left, expr.right);
@@ -37,16 +54,23 @@ class AstPrinter implements Expr.Visitor<String> {
 
     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));
-  // }
+  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)));
+    Token varToken = new Token(TokenType.IDENTIFIER,"drink","tea",0);
+    Expr varExpr = new Expr.Variable(varToken);
+    Expr assignExpr = new Expr.Assign(
+      varToken
+      ,new Expr.Literal("\"cola\"")
+    );
+    System.out.println(new AstPrinter().print(expression));
+    System.out.println(new AstPrinter().print(varExpr));
+    System.out.println(new AstPrinter().print(assignExpr));
+  }
 
 }

src/com/lox/Expr.java

@@ -4,10 +4,26 @@ import java.util.List;
 
 abstract class Expr {
   interface Visitor<R> {
+    R visitAssignExpr(Assign expr);
     R visitBinaryExpr(Binary expr);
     R visitGroupingExpr(Grouping expr);
     R visitLiteralExpr(Literal expr);
     R visitUnaryExpr(Unary expr);
+    R visitVariableExpr(Variable expr);
+  }
+  static class Assign extends Expr {
+    Assign(Token name, Expr value) {
+      this.name = name;
+      this.value = value;
+    }
+
+    @Override
+    <R> R accept(Visitor<R> visitor) {
+      return visitor.visitAssignExpr(this);
+    }
+
+    final Token name;
+    final Expr value;
   }
   static class Binary extends Expr {
     Binary(Expr left, Token operator, Expr right) {
@@ -63,6 +79,18 @@ abstract class Expr {
     final Token operator;
     final Expr right;
   }
+  static class Variable extends Expr {
+    Variable(Token name) {
+      this.name = name;
+    }
+
+    @Override
+    <R> R accept(Visitor<R> visitor) {
+      return visitor.visitVariableExpr(this);
+    }
+
+    final Token name;
+  }
 
   abstract <R> R accept(Visitor<R> visitor);
-}
+}

src/com/lox/Stmt.java

@@ -4,8 +4,22 @@ import java.util.List;
 
 abstract class Stmt {
   interface Visitor<R> {
+    R visitBlockStmt(Block stmt);
     R visitExpressionStmt(Expression stmt);
     R visitPrintStmt(Print stmt);
+    R visitVarStmt(Var stmt);
+  }
+  static class Block extends Stmt {
+    Block(List<Stmt> statements) {
+      this.statements = statements;
+    }
+
+    @Override
+    <R> R accept(Visitor<R> visitor) {
+      return visitor.visitBlockStmt(this);
+    }
+
+    final List<Stmt> statements;
   }
   static class Expression extends Stmt {
     Expression(Expr expression) {
@@ -31,6 +45,20 @@ abstract class Stmt {
 
     final Expr expression;
   }
+  static class Var extends Stmt {
+    Var(Token name, Expr initializer) {
+      this.name = name;
+      this.initializer = initializer;
+    }
+
+    @Override
+    <R> R accept(Visitor<R> visitor) {
+      return visitor.visitVarStmt(this);
+    }
+
+    final Token name;
+    final Expr initializer;
+  }
 
   abstract <R> R accept(Visitor<R> visitor);
 }