From 20aae726fa959272ed1568b39b78a0ff501b4882 Mon Sep 17 00:00:00 2001
From: Yann Herklotz <git@yannherklotz.com>
Date: Sat, 24 Sep 2022 18:37:04 +0100
Subject: Add more monads

---
 src/common/Optionmonad.v | 12 +++++++++++-
 1 file changed, 11 insertions(+), 1 deletion(-)

(limited to 'src/common/Optionmonad.v')

diff --git a/src/common/Optionmonad.v b/src/common/Optionmonad.v
index 14a41ef..4a80ff8 100644
--- a/src/common/Optionmonad.v
+++ b/src/common/Optionmonad.v
@@ -63,4 +63,14 @@ Module Option <: Monad.
 
 End Option.
 
-Module OptionExtra := MonadExtra(Option).
+Module OptionExtra.
+  Module OE := MonadExtra(Option).
+  Export OE.
+
+  Lemma mfold_left_Some :
+    forall A B f x n y,
+      @mfold_left A B f x n = Some y ->
+      exists n', n = Some n'.
+  Proof. induction x; intros; destruct n; eauto. Qed.
+
+End OptionExtra.
-- 
cgit