From 41d2d56d67046ee56a8ba29b126f333ef38d2765 Mon Sep 17 00:00:00 2001
From: Alexey Radul <axch@mit.edu>
Date: Wed, 22 May 2013 23:45:42 -0400
Subject: [PATCH] Explain the use of the token in try-rules.

---
 pattern-dispatch.scm | 1 +
 1 file changed, 1 insertion(+)

diff --git a/pattern-dispatch.scm b/pattern-dispatch.scm
index c76d691..ba19691 100644
--- a/pattern-dispatch.scm
+++ b/pattern-dispatch.scm
@@ -42,6 +42,7 @@
       (if (null? rules)
           (fail)
           (let ((answer ((car rules) data token)))
+            ;; Distinguish failure from idempotent success
             (if (eq? answer token)
                 (per-rule (cdr rules))
                 answer))))))