From c3eeb29940c5b59e369942d9db11e01c240b4ba3 Mon Sep 17 00:00:00 2001
From: Michael Martin-Smucker <mlmartin13@gmail.com>
Date: Thu, 2 Nov 2017 13:26:25 -0600
Subject: [PATCH 1/2] Avoid infinite loop possibility with takeEnd

---
 src/Data/List.purs       | 2 +-
 test/Test/Data/List.purs | 4 +++-
 2 files changed, 4 insertions(+), 2 deletions(-)

diff --git a/src/Data/List.purs b/src/Data/List.purs
index d575c84..1b0b300 100644
--- a/src/Data/List.purs
+++ b/src/Data/List.purs
@@ -541,7 +541,7 @@ takeWhile p = go Nil
 -- |
 -- | Running time: `O(n)` where `n` is the number of elements to drop.
 drop :: forall a. Int -> List a -> List a
-drop 0 xs = xs
+drop n xs | n < 1 = xs
 drop _ Nil = Nil
 drop n (x : xs) = drop (n - 1) xs
 
diff --git a/test/Test/Data/List.purs b/test/Test/Data/List.purs
index f476dc3..e584dab 100644
--- a/test/Test/Data/List.purs
+++ b/test/Test/Data/List.purs
@@ -230,16 +230,18 @@ testList = do
   assert $ (takeEnd 1 (l [1, 2, 3])) == l [3]
   assert $ (takeEnd 2 (l [1, 2, 3])) == l [2, 3]
   assert $ (takeEnd 1 nil) == nil
+  assert $ (takeEnd 2 (l [1])) == l [1]
 
   log "takeWhile should keep all values that match a predicate from the front of an list"
   assert $ (takeWhile (_ /= 2) (l [1, 2, 3])) == l [1]
   assert $ (takeWhile (_ /= 3) (l [1, 2, 3])) == l [1, 2]
   assert $ (takeWhile (_ /= 1) nil) == nil
 
-  log "dropE should remove the specified number of items from the front of an list"
+  log "drop should remove the specified number of items from the front of an list"
   assert $ (drop 1 (l [1, 2, 3])) == l [2, 3]
   assert $ (drop 2 (l [1, 2, 3])) == l [3]
   assert $ (drop 1 nil) == nil
+  assert $ (drop (-1) (l [1, 2, 3])) == l [1, 2, 3]
 
   log "dropEnd should remove the specified number of items from the end of an list"
   assert $ (dropEnd 1 (l [1, 2, 3])) == l [1, 2]

From c26dc1d2cf067659f263b63a37f693e5bf74c583 Mon Sep 17 00:00:00 2001
From: Michael Martin-Smucker <mlmartin13@gmail.com>
Date: Thu, 2 Nov 2017 17:29:22 -0600
Subject: [PATCH 2/2] Protect `take` against infinite recursion

---
 src/Data/List.purs       | 2 +-
 test/Test/Data/List.purs | 2 ++
 2 files changed, 3 insertions(+), 1 deletion(-)

diff --git a/src/Data/List.purs b/src/Data/List.purs
index 1b0b300..afc2160 100644
--- a/src/Data/List.purs
+++ b/src/Data/List.purs
@@ -517,7 +517,7 @@ slice start end xs = take (end - start) (drop start xs)
 take :: forall a. Int -> List a -> List a
 take = go Nil
   where
-  go acc 0 _ = reverse acc
+  go acc n _ | n < 1 = reverse acc
   go acc _ Nil = reverse acc
   go acc n (x : xs) = go (x : acc) (n - 1) xs
 
diff --git a/test/Test/Data/List.purs b/test/Test/Data/List.purs
index e584dab..42d84c4 100644
--- a/test/Test/Data/List.purs
+++ b/test/Test/Data/List.purs
@@ -225,6 +225,8 @@ testList = do
   assert $ (take 1 (l [1, 2, 3])) == l [1]
   assert $ (take 2 (l [1, 2, 3])) == l [1, 2]
   assert $ (take 1 nil) == nil
+  assert $ (take 0 (l [1, 2])) == l []
+  assert $ (take (-1) (l [1, 2])) == l []
 
   log "takeEnd should keep the specified number of items from the end of an list, discarding the rest"
   assert $ (takeEnd 1 (l [1, 2, 3])) == l [3]