From 6444357444918fea80fbec4c6104c592e3bd5038 Mon Sep 17 00:00:00 2001
From: MatMoul <matmoul@gmail.com>
Date: Fri, 15 May 2026 20:47:19 +0200
Subject: [PATCH] fix: ignore backspace when the stack is empty

---
 .memory/state.md         | 2 +-
 samples/calc-02/index.js | 3 ++-
 2 files changed, 3 insertions(+), 2 deletions(-)

diff --git a/.memory/state.md b/.memory/state.md
index a3839b9..389d398 100644
--- a/.memory/state.md
+++ b/.memory/state.md
@@ -5,5 +5,5 @@
 - Public API: `push`, `pop`, `clear`, `swap`, `remove`, `edit`, `isValidIndex`, `input`, `command`, `getOperationsByCategory`, `getConstants`
 - Config: `maxSize`, `base`, `angleMode`, `enabledCommands`
 - Commands: arithmetic, stack, trigonometry, constants `pi` and `e`
-- Demo actions: paste now parses clipboard text as a number before pushing it to the stack; Ctrl+V is supported via the hidden input paste event
+- Demo actions: paste now parses clipboard text as a number before pushing it to the stack; Ctrl+V is supported via the hidden input paste event; backspace is ignored when the stack is empty
 - Exports: browser `window.RpnCalculator`, CommonJS `module.exports`
diff --git a/samples/calc-02/index.js b/samples/calc-02/index.js
index 169da61..53d168b 100644
--- a/samples/calc-02/index.js
+++ b/samples/calc-02/index.js
@@ -162,9 +162,10 @@ function execute(name) {
 		} else if (name === 'backspace') {
 			if (calc.isEditing) {
 				inputToX('Backspace');
-			} else {
+			} else if (calc.isValidIndex(0)) {
 				calc.remove(0);
 			}
+
 		} else if (name === 'swap') {
 			pushEditingValueIfNeeded();
 			if (calc.isValidIndex(1)) {