Add while statement

src/com/craftinginterpreters/lox/Interpreter.java

@@ -157,6 +157,15 @@ class Interpreter implements Expr.Visitor<Object>, Stmt.Visitor<Void> {
         return null;
     }
 
+    @Override
+    public Void visitWhileStmt(Stmt.While stmt) {
+        while (isTruthy(evaluate(stmt.condition))) {
+            execute(stmt.body);
+        }
+
+        return null;
+    }
+
     @Override
     public Object visitAssignExpr(Expr.Assign expr) {
         Object value = evaluate(expr.value);

src/com/craftinginterpreters/lox/Parser.java

@@ -47,6 +47,8 @@ class Parser {
             return ifStatement();
         if (match(PRINT))
             return printStatement();
+        if (match(WHILE))
+            return whileStatement();
         if (match(LEFT_BRACE))
             return new Stmt.Block(block());
 
@@ -85,6 +87,15 @@ class Parser {
         return new Stmt.Var(name, initializer);
     }
 
+    private Stmt whileStatement() {
+        consume(LEFT_PAREN, "Expect '(' after 'while'.");
+        Expr condition = expression();
+        consume(RIGHT_PAREN, "Expect ')' after condition.");
+        Stmt body = statement();
+
+        return new Stmt.While(condition, body);
+    }
+
     private Stmt expressionStatement() {
         Expr expr = expression();
         consume(SEMICOLON, "Expect ';' after expression.");

src/com/craftinginterpreters/tool/GenerateAst.java

@@ -22,7 +22,7 @@ public class GenerateAst {
         defineAst(outputDir, "Stmt",
                 Arrays.asList("Block : List<Stmt> statements", "Expression : Expr expression",
                         "If : Expr condition, Stmt thenBranch, Stmt elseBranch", "Print : Expr expression",
-                        "Var : Token name, Expr initializer"));
+                        "Var : Token name, Expr initializer", "While : Expr condition, Stmt body"));
     }
 
     private static void defineAst(String outputDir, String baseName, List<String> types) throws IOException {