From 38be469fe11f94124f98fd25046cfc31278b3594 Mon Sep 17 00:00:00 2001
From: Max Willsey <me@mwillsey.com>
Date: Fri, 9 Feb 2024 13:59:49 -0800
Subject: [PATCH] Add note in is_not_zero example.

Closes #297
---
 src/macros.rs | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/src/macros.rs b/src/macros.rs
index 58afca0e..ac39e2ec 100644
--- a/src/macros.rs
+++ b/src/macros.rs
@@ -281,6 +281,9 @@ impl Applier<SimpleLanguage, ()> for MySillyApplier {
 fn is_not_zero(var: &'static str) -> impl Fn(&mut EGraph, Id, &Subst) -> bool {
     let var = var.parse().unwrap();
     let zero = SimpleLanguage::Num(0);
+    // note this check is just an example,
+    // checking for the absence of 0 is insufficient since 0 could be merged in later
+    // see https://github.com/egraphs-good/egg/issues/297
     move |egraph, _, subst| !egraph[subst[var]].nodes.contains(&zero)
 }
 ```