Merge branch 'master' into master

1 files changed, 25 insertions, 11 deletions

diff --git a/numpy/lib/stride_tricks.py b/numpy/lib/stride_tricks.py
index ca13738c1..8aafd094b 100644
--- a/numpy/lib/stride_tricks.py
+++ b/numpy/lib/stride_tricks.py
@@ -8,6 +8,7 @@ NumPy reference guide.
 from __future__ import division, absolute_import, print_function
 
 import numpy as np
+from numpy.core.overrides import array_function_dispatch
 
 __all__ = ['broadcast_to', 'broadcast_arrays']
 
@@ -120,21 +121,26 @@ def _broadcast_to(array, shape, subok, readonly):
     if any(size < 0 for size in shape):
         raise ValueError('all elements of broadcast shape must be non-'
                          'negative')
-    needs_writeable = not readonly and array.flags.writeable
-    extras = ['reduce_ok'] if needs_writeable else []
-    op_flag = 'readwrite' if needs_writeable else 'readonly'
+    extras = []
     it = np.nditer(
         (array,), flags=['multi_index', 'refs_ok', 'zerosize_ok'] + extras,
-        op_flags=[op_flag], itershape=shape, order='C')
+        op_flags=['readonly'], itershape=shape, order='C')
     with it:
         # never really has writebackifcopy semantics
         broadcast = it.itviews[0]
     result = _maybe_view_as_subclass(array, broadcast)
-    if needs_writeable and not result.flags.writeable:
+    # In a future version this will go away
+    if not readonly and array.flags._writeable_no_warn:
         result.flags.writeable = True
+        result.flags._warn_on_write = True
     return result
 
 
+def _broadcast_to_dispatcher(array, shape, subok=None):
+    return (array,)
+
+
+@array_function_dispatch(_broadcast_to_dispatcher, module='numpy')
 def broadcast_to(array, shape, subok=False):
     """Broadcast an array to a new shape.
 
@@ -180,8 +186,6 @@ def _broadcast_shape(*args):
     """Returns the shape of the arrays that would result from broadcasting the
     supplied arrays against each other.
     """
-    if not args:
-        return ()
     # use the old-iterator because np.nditer does not handle size 0 arrays
     # consistently
     b = np.broadcast(*args[:32])
@@ -195,6 +199,11 @@ def _broadcast_shape(*args):
     return b.shape
 
 
+def _broadcast_arrays_dispatcher(*args, **kwargs):
+    return args
+
+
+@array_function_dispatch(_broadcast_arrays_dispatcher, module='numpy')
 def broadcast_arrays(*args, **kwargs):
     """
     Broadcast any number of arrays against each other.
@@ -213,8 +222,15 @@ def broadcast_arrays(*args, **kwargs):
     broadcasted : list of arrays
         These arrays are views on the original arrays.  They are typically
         not contiguous.  Furthermore, more than one element of a
-        broadcasted array may refer to a single memory location.  If you
-        need to write to the arrays, make copies first.
+        broadcasted array may refer to a single memory location. If you need
+        to write to the arrays, make copies first. While you can set the
+        ``writable`` flag True, writing to a single output value may end up
+        changing more than one location in the output array.
+
+        .. deprecated:: 1.17
+            The output is currently marked so that if written to, a deprecation
+            warning will be emitted. A future version will set the
+            ``writable`` flag False so writing to it will raise an error.
 
     Examples
     --------
@@ -251,7 +267,5 @@ def broadcast_arrays(*args, **kwargs):
         # Common case where nothing needs to be broadcasted.
         return args
 
-    # TODO: consider making the results of broadcast_arrays readonly to match
-    # broadcast_to. This will require a deprecation cycle.
     return [_broadcast_to(array, shape, subok=subok, readonly=False)
             for array in args]