Hi Todd,

I agree a flag is more suitable than classes.

I would add another bonus of a flag than a function argument is to avoid massive contamination of function signatures for a global variation of behavior that affects many functions. 

Yu

On Wed, Jan 9, 2019 at 11:34 PM Todd <toddrjen@gmail.com> wrote:

On Mon, Jan 7, 2019, 14:22 Feng Yu <rainwoodman@gmail.com wrote:

Hi,

Was it ever brought up the possibility of a new array class (ndrefonly, ndview) that is strictly no copy?

All operations on ndrefonly will return ndrefonly and if the operation cannot be completed without making a copy, it shall throw an error.

On the implementation there are two choices if we use subclasses:

- ndrefonly can be a subclass of ndarray. The pattern would be subclass limiting functionality of super, but ndrefonly is a ndarray.

- ndarray as a subclass of ndarray. Subclass supplements functionality of super. : ndarray will not throw an error when a copy is necessary. However ndarray is not a ndarray.

If we want to be wild they do not even need to be subclasses of each other, or maybe they shall both be subclasses of something more fundamental.

- Yu

I would prefer a flag for this.  Someone can make an array read-only by setting `arr.flags.writable=False`.  So along those lines, we could have a `arr.flags.copyable` flag that if set to `False` would result in an error of any operation tried to copy the data.

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