ENH: Allow for a flatiter index on a flatiter object #27342
Description
Proposed new feature or change:
Currently, indexing a flatiter with an array object and vice-versa is permitted.
In [1]: a = np.arange(9).reshape((3, 3))
In [2]: a
Out[2]:
array([[0, 1, 2],
[3, 4, 5],
[6, 7, 8]])
In [3]: b = np.array([0, 4, 5, 7])
In [4]: b
Out[4]: array([0, 4, 5, 7])
In [5]: a.flat[b]
Out[5]: array([0, 4, 5, 7])
In [6]: a = np.arange(9)
In [7]: a
Out[7]: array([0, 1, 2, 3, 4, 5, 6, 7, 8])
In [8]: a[b.flat]
Out[8]: array([0, 4, 5, 7])However, indexing a flatiter with a flatiter results in an exception:
In [9]: a.flat[b.flat]
---------------------------------------------------------------------------
IndexError Traceback (most recent call last)
Cell In[9], line 1
----> 1 a.flat[b.flat]
IndexError: unsupported iterator indexIt would be relatively straightforward to allow flatiter objects to be index by other flatiter objects as well, and it seems that there's no downsides to this. Thoughts?