From 3b9c44434e8bc395068eb8c3e319e384b66ed72e Mon Sep 17 00:00:00 2001
From: Tom Willemse
Date: Sat, 16 Jan 2021 22:16:31 -0800
Subject: Add while statement

---
 src/com/craftinginterpreters/lox/Interpreter.java  |  9 +++++++++
 src/com/craftinginterpreters/lox/Parser.java       | 11 +++++++++++
 src/com/craftinginterpreters/tool/GenerateAst.java |  2 +-
 3 files changed, 21 insertions(+), 1 deletion(-)

diff --git a/src/com/craftinginterpreters/lox/Interpreter.java b/src/com/craftinginterpreters/lox/Interpreter.java
index 6c32233..6b3e409 100644
--- a/src/com/craftinginterpreters/lox/Interpreter.java
+++ b/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);
diff --git a/src/com/craftinginterpreters/lox/Parser.java b/src/com/craftinginterpreters/lox/Parser.java
index 1643129..a85d70f 100644
--- a/src/com/craftinginterpreters/lox/Parser.java
+++ b/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.");
diff --git a/src/com/craftinginterpreters/tool/GenerateAst.java b/src/com/craftinginterpreters/tool/GenerateAst.java
index a3935e1..8845c6e 100644
--- a/src/com/craftinginterpreters/tool/GenerateAst.java
+++ b/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 {
-- 
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