From 1926a5e69ecd859a0ad01d85ef548357491f044f Mon Sep 17 00:00:00 2001
From: Ingo Wechsung <ingo.wechsung@gmail.com>
Date: Thu, 10 May 2018 13:20:43 +0200
Subject: [PATCH] fix #357

---
 tests/comp/Issue357.fr | 13 +++++++++++++
 1 file changed, 13 insertions(+)
 create mode 100644 tests/comp/Issue357.fr

diff --git a/tests/comp/Issue357.fr b/tests/comp/Issue357.fr
new file mode 100644
index 00000000..f4e053f6
--- /dev/null
+++ b/tests/comp/Issue357.fr
@@ -0,0 +1,13 @@
+{-- 
+    As outlined in 'https://github.com/Frege/frege/issues/357 #357',
+    the compiler decides that 'myFoldM' should be strict, despite the tail call
+    'Maybe.>>=' returns lazy. This is unfortunate, because the recursion happens
+    on the stack, instead through a Thunk returned by >>=
+-}
+module tests.comp.Issue357 where
+
+myFoldM :: (b -> a -> Maybe b) -> b -> [a] -> Maybe b
+myFoldM f z (x:xs) = f z x >>= \acc -> myFoldM f acc xs
+myFoldM _ z []     = pure z
+
+main = println $ myFoldM (\r _ -> Just $! succ r) 0 [1..5000]