From 9a90abf995d0d8d9e96992a083dc55a41a93254f Mon Sep 17 00:00:00 2001
From: MattHarrigan <harrigan.matthew@gmail.com>
Date: Thu, 27 Oct 2016 19:38:01 -0400
Subject: BUG: return subclasses from ediff1d

---
 numpy/lib/arraysetops.py | 25 ++++++++++++-------------
 1 file changed, 12 insertions(+), 13 deletions(-)

(limited to 'numpy/lib/arraysetops.py')

diff --git a/numpy/lib/arraysetops.py b/numpy/lib/arraysetops.py
index 889415efe..836f4583f 100644
--- a/numpy/lib/arraysetops.py
+++ b/numpy/lib/arraysetops.py
@@ -85,28 +85,27 @@ def ediff1d(ary, to_end=None, to_begin=None):
     if to_begin is None and to_end is None:
         return ary[1:] - ary[:-1]
 
-    # get the length of the diff'd values
-    l = len(ary) - 1
-    if l < 0:
-        # force length to be non negative, match previous API
-        # should this be an warning or deprecated?
-        l = 0
-
     if to_begin is None:
-        to_begin = np.array([])
+        l_begin = 0
     else:
         to_begin = np.asanyarray(to_begin).ravel()
+        l_begin = len(to_begin)
 
     if to_end is None:
-        to_end = np.array([])
+        l_end = 0
     else:
         to_end = np.asanyarray(to_end).ravel()
+        l_end = len(to_end)
 
     # do the calculation in place and copy to_begin and to_end
-    result = np.empty(l + len(to_begin) + len(to_end), dtype=ary.dtype)
-    result[:len(to_begin)] = to_begin
-    result[len(to_begin) + l:] = to_end
-    np.subtract(ary[1:], ary[:-1], result[len(to_begin):len(to_begin) + l])
+    l_diff = max(len(ary) - 1, 0)
+    result = np.empty(l_diff + l_begin + l_end, dtype=ary.dtype)
+    result = ary.__array_wrap__(result)
+    if l_begin > 0:
+        result[:l_begin] = to_begin
+    if l_end > 0:
+        result[l_begin + l_diff:] = to_end
+    np.subtract(ary[1:], ary[:-1], result[l_begin:l_begin + l_diff])
     return result
 
 
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