0-dim memory is indexed by x[()]. The ctypes example has an additional
problem, because format="<d" is not yet implemented in memoryview.

Only native single character formats in struct module syntax are
implemented, and "<d" in struct module syntax means "standard size,
little endian".

To demonstrate 0-dim indexing, here's an example using _testbuffer:

>>> x = ndarray(3.14, shape=[], format='d', flags=ND_WRITABLE)
>>> x[()]
3.14
>>> tau = 6.28
>>> x[()] = tau
>>> x[()]
6.28
>>> m = memoryview(x)
>>> m[()]
6.28
>>> m[()] = 100.111
>>> m[()]
100.111