add scopes
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b1cd274a39
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e4f2519891
@ -33,6 +33,11 @@ class ASTPrinter implements Expr.Visitor<String> {
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return expr.name.toString();
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return expr.name.toString();
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}
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}
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@Override
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public String visitAssignExpr(Expr.Assign expr) {
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return expr.name.toString();
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}
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private String parenthesize(String name, Expr... exprs) {
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private String parenthesize(String name, Expr... exprs) {
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StringBuilder builder = new StringBuilder();
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StringBuilder builder = new StringBuilder();
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@ -4,16 +4,44 @@ import java.util.HashMap;
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import java.util.Map;
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import java.util.Map;
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class Environment {
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class Environment {
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final Environment enclosing;
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private final Map<String, Object> values = new HashMap<>();
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private final Map<String, Object> values = new HashMap<>();
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Environment() {
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enclosing = null;
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}
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Environment(Environment enclosing) {
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this.enclosing = enclosing;
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}
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void define(String name, Object value) {
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void define(String name, Object value) {
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values.put(name, value);
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values.put(name, value);
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}
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}
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void assign(Token name, Object value) {
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if (values.containsKey(name.lexeme)) {
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values.put(name.lexeme, value);
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return;
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}
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if (enclosing != null) {
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enclosing.assign(name, value);
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return;
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}
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throw new RuntimeError(name, "Undefined variable '" + name.lexeme + "'.");
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}
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Object get(Token name) {
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Object get(Token name) {
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if (values.containsKey(name.lexeme)) {
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if (values.containsKey(name.lexeme)) {
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return values.get(name.lexeme);
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return values.get(name.lexeme);
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}
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}
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if (enclosing != null) {
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return enclosing.get(name);
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}
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throw new RuntimeError(name, "Undefined variable '" + name.lexeme + "'.");
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throw new RuntimeError(name, "Undefined variable '" + name.lexeme + "'.");
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}
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}
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}
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}
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@ -1,7 +1,10 @@
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package lox;
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package lox;
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import java.util.List;
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abstract class Expr {
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abstract class Expr {
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interface Visitor<R> {
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interface Visitor<R> {
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R visitAssignExpr(Assign expr);
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R visitBinaryExpr(Binary expr);
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R visitBinaryExpr(Binary expr);
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R visitGroupingExpr(Grouping expr);
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R visitGroupingExpr(Grouping expr);
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R visitLiteralExpr(Literal expr);
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R visitLiteralExpr(Literal expr);
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@ -9,6 +12,21 @@ abstract class Expr {
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R visitVariableExpr(Variable expr);
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R visitVariableExpr(Variable expr);
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}
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}
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static class Assign extends Expr {
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Assign(Token name, Expr value) {
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this.name = name;
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this.value = value;
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}
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@Override
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<R> R accept(Visitor<R> visitor) {
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return visitor.visitAssignExpr(this);
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}
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final Token name;
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final Expr value;
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}
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static class Binary extends Expr {
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static class Binary extends Expr {
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Binary(Expr left, Token operator, Expr right) {
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Binary(Expr left, Token operator, Expr right) {
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this.left = left;
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this.left = left;
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@ -89,6 +89,13 @@ class Interpreter implements Expr.Visitor<Object>, Stmt.Visitor<Void> {
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return environment.get(expr.name);
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return environment.get(expr.name);
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}
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}
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@Override
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public Object visitAssignExpr(Expr.Assign expr) {
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Object value = evaluate(expr.value);
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environment.assign(expr.name, value);
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return value;
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}
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@Override
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@Override
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public Void visitExpressionStmt(Stmt.Expression stmt) {
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public Void visitExpressionStmt(Stmt.Expression stmt) {
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evaluate(stmt.expression);
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evaluate(stmt.expression);
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@ -112,6 +119,12 @@ class Interpreter implements Expr.Visitor<Object>, Stmt.Visitor<Void> {
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return null;
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return null;
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}
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}
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@Override
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public Void visitBlockStmt(Stmt.Block stmt) {
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executeBlock(stmt.statements, new Environment(environment));
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return null;
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}
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private void checkNumberOperand(Token operator, Object operand) {
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private void checkNumberOperand(Token operator, Object operand) {
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if (operand instanceof Double) {
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if (operand instanceof Double) {
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return;
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return;
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@ -167,4 +180,18 @@ class Interpreter implements Expr.Visitor<Object>, Stmt.Visitor<Void> {
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private void execute(Stmt stmt) {
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private void execute(Stmt stmt) {
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stmt.accept(this);
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stmt.accept(this);
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}
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}
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void executeBlock(List<Stmt> statements, Environment environment) {
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Environment previous = this.environment;
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try {
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this.environment = environment;
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for (Stmt statement : statements) {
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// could also just redesign this to accept an environment field everywhere
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execute(statement);
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}
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} finally {
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this.environment = previous;
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}
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}
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}
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}
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@ -50,6 +50,9 @@ class Parser {
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if (match(PRINT)) {
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if (match(PRINT)) {
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return printStatement();
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return printStatement();
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}
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}
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if (match(LEFT_BRACE)) {
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return new Stmt.Block(block());
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}
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return expressionStatement();
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return expressionStatement();
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}
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}
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@ -65,8 +68,35 @@ class Parser {
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return new Stmt.Expression(value);
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return new Stmt.Expression(value);
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}
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}
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private List<Stmt> block() {
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List<Stmt> statements = new ArrayList<>();
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while (!check(RIGHT_BRACE) && !isAtEnd()) {
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statements.add(declaration());
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}
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consume(RIGHT_BRACE, "Expect '}' after block.");
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return statements;
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}
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private Expr assignment() {
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Expr expr = equality();
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if (match(EQUAL)) {
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Token equals = previous();
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Expr value = assignment();
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if (expr instanceof Expr.Variable) {
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Token name = ((Expr.Variable)expr).name;
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return new Expr.Assign(name, value);
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}
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// does not throw because parsing _can_ continue
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error(equals, "Invalid assignment target.");
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}
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return expr;
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}
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private Expr expression() {
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private Expr expression() {
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return equality();
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return assignment();
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}
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}
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private Expr equality() {
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private Expr equality() {
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@ -1,12 +1,28 @@
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package lox;
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package lox;
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import java.util.List;
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abstract class Stmt {
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abstract class Stmt {
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interface Visitor<R> {
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interface Visitor<R> {
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R visitBlockStmt(Block stmt);
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R visitExpressionStmt(Expression stmt);
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R visitExpressionStmt(Expression stmt);
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R visitVarStmt(Var stmt);
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R visitVarStmt(Var stmt);
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R visitPrintStmt(Print stmt);
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R visitPrintStmt(Print stmt);
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}
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}
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static class Block extends Stmt {
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Block(List<Stmt> statements) {
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this.statements = statements;
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}
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@Override
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<R> R accept(Visitor<R> visitor) {
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return visitor.visitBlockStmt(this);
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}
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final List<Stmt> statements;
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}
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static class Expression extends Stmt {
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static class Expression extends Stmt {
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Expression(Expr expression) {
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Expression(Expr expression) {
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this.expression = expression;
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this.expression = expression;
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@ -1,5 +1,6 @@
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package tool;
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package tool;
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import java.io.File;
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import java.io.IOException;
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import java.io.IOException;
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import java.io.PrintWriter;
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import java.io.PrintWriter;
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import java.nio.charset.Charset;
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import java.nio.charset.Charset;
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@ -17,30 +18,32 @@ public class GenerateAST {
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outputDir,
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outputDir,
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"Expr",
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"Expr",
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Arrays.asList(
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Arrays.asList(
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"Binary : Expr left, Token operator, Expr right",
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"Assign : Token name, Expr value",
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"Binary : Expr left, Token operator, Expr right",
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"Grouping : Expr expression",
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"Grouping : Expr expression",
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"Literal : Object value",
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"Literal : Object value",
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"Unary : Token operator, Expr right",
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"Unary : Token operator, Expr right",
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"Variable : Token name"));
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"Variable : Token name"));
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defineAST(
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defineAST(
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outputDir,
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outputDir,
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"Stmt",
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"Stmt",
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Arrays.asList(
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Arrays.asList(
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"Block : List<Stmt> statements",
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"Expression : Expr expression",
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"Expression : Expr expression",
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"Var : Token name, Expr initializer",
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"Var : Token name, Expr initializer",
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"Print : Expr expression"));
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"Print : Expr expression"));
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}
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}
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private static void defineAST(String outputDir, String baseName, List<String> types)
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private static void defineAST(String outputDir, String baseName, List<String> types)
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throws IOException {
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throws IOException {
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String path = outputDir + "/" + baseName + ".java";
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String path = outputDir + File.separator + baseName + ".java";
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PrintWriter writer = new PrintWriter(path, Charset.defaultCharset());
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PrintWriter writer = new PrintWriter(path, Charset.defaultCharset());
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writer.println("package lox;");
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writer.println("package lox;");
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writer.println();
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writer.println();
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// writer.println("import java.util.List;");
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writer.println("import java.util.List;");
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// writer.println();
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writer.println();
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writer.println("abstract class " + baseName + " {");
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writer.println("abstract class " + baseName + " {");
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defineVisitor(writer, baseName, types);
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defineVisitor(writer, baseName, types);
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