From f91c0bf56ba1ed979266d4e32937dcab48d7030e Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Hugo=20H=C3=B6rnquist?= <hugo@lysator.liu.se>
Date: Mon, 18 Mar 2019 18:44:04 +0100
Subject: Add equal? instance to <optional>.

---
 monad/optional.scm | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/monad/optional.scm b/monad/optional.scm
index 1aa1e92..015fc90 100644
--- a/monad/optional.scm
+++ b/monad/optional.scm
@@ -51,3 +51,10 @@ the value embedded in maybe-val"
            (($ <optional> slot) (proc slot))))))
 
 (define-method (return (a <optional>)) just)
+
+(define-method (equal? (a <optional>)
+                       (b <optional>))
+  (or (and (nothing? a) (nothing? b))
+      (from-just #f (do aa <- a
+                        bb <- b
+                        (just (equal? aa bb))))))
-- 
cgit v1.2.3