DEP: Deprecate np.MachAr

[BvB93]

This PR deprecates the np.MachAr class, the matching np.core.machar module and np.finfo.machar attribute.

As an alternative it is recommended to use to directly grab the property of interest from the np.finfo instance.

Note that the module is technically private, but with the lack of underscores it's better to be safe than sorry.

[seberg]

Is there any use for finfo.machar? Can we just include that in the deprecation (i.e. make it a private variable if we still need it)?

[BvB93]

Is there any use for finfo.machar?

There are a few MachAr attributes that are not exposed to finfo.
Some are available under a different name (xmin -> min), but others (ibeta) would have to be added.

In [11]: import numpy as np

In [12]: finfo_f8 = np.finfo(np.float64)
    ...: machar_f8 = np.MachAr(np.float64)

In [14]: set(dir(machar_f8)) - set(dir(finfo_f8))
Out[14]: 
{'_do_init',
 '_str_xmax',
 '_str_xmin',
 'epsilon',
 'huge',
 'ibeta',
 'irnd',
 'it',
 'ngrd',
 'title',
 'xmax',
 'xmin'}

[seberg]

Hmm, fair point. On some of these, I would be willing to just gamble that nobody uses them anyway, i.e. ibeta is always 2. Some seem like they might be interesting on weird platforms/settings (irnd or ngrd) though, I tend to trying getting rid of them, but not sure.

[BvB93]

Ah well, let's give deprecating finfo.machar a shot.

[charris]

Thanks Bas.