finfo should not require float type for the result fields

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Assessment

Difficulty
5/5
Estimated time
Over a week
Newbie friendliness
35/100
Issue type
Feature
Clarity
Mostly clear
Activity status
Stale
Tech stack
numpy, python
Domain
documentation

Research direction

Start with the linked finfo specification and compare its required result types with the NumPy examples in the issue. Clarify whether finfo alone or both finfo and iinfo should return 0-D arrays, then update the specification so the chosen behavior and completion criteria are explicit.

Written by the indexing model from the issue text.

Description

API change

Right now finfo requires that the output fields be float https://data-apis.org/array-api/latest/API_specification/generated/signatures.data_type_functions.finfo.html#signatures.data_type_functions.finfo. However, making the results 0-D arrays would be better.

For the spec itself, float is fine, but it's problematic for any library that implements higher precision data types like float128:

>>> import numpy as np
>>> np.finfo(np.float128)
finfo(resolution=1.0000000000000000715e-18, min=-1.189731495357231765e+4932, max=1.189731495357231765e+4932, dtype=float128)
>>> float('-1.189731495357231765e+4932')
-inf

float is essentially a float64, so the various values for float128 cannot be represented as floats. NumPy uses scalars for the values, which for the spec would be 0-D arrays:

>>> type(np.finfo(np.float128).min)
<class 'numpy.float128'>

Even if there are no plans to add float128 to the spec, it's useful for libraries that do have it to have a consistent return type for finfo, since float and a 0-D array aren't 100% duck type compatible.

For iinfo obviously this problem isn't present since int can represent any integer, but it may be good to change it to 0-D array as well just for consistency (although I should note that numpy.iinfo just uses int for its fields).

Dominant language
Python
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