From 9b9bfa5572e0ebb791621bf341e28e498da638b9 Mon Sep 17 00:00:00 2001
From: Brian McKenna <bmckenna@atlassian.com>
Date: Thu, 7 Jul 2016 15:35:51 +1000
Subject: [PATCH] Add spanM

---
 src/Control/Monad/Loops.hs | 11 +++++++++++
 1 file changed, 11 insertions(+)

diff --git a/src/Control/Monad/Loops.hs b/src/Control/Monad/Loops.hs
index 409bcd6..a365245 100644
--- a/src/Control/Monad/Loops.hs
+++ b/src/Control/Monad/Loops.hs
@@ -385,6 +385,17 @@ dropWhileM p (x:xs) = do
                 then dropWhileM p xs
                 else return (x:xs)
 
+-- | Monad 'span'.
+spanM :: (Monad m) => (a -> m Bool) -> [a] -> m ([a], [a])
+spanM _ [] = return []
+spanM p xs@(x:xs') = do
+        q <- p x
+        if q
+                then do
+                  (ys, zs) <- spanM p xs'
+                  return (x:ys, zs)
+                else return ([], xs)
+
 -- |like 'dropWhileM' but trims both ends of the list.
 trimM :: (Monad m) => (a -> m Bool) -> [a] -> m [a]
 trimM p xs = do