`diff` to allow Python scalar or 0d array `append` and `prepend`?
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Assessment
- Difficulty
- 5/5
- Estimated time
- Over a week
- Newbie friendliness
- 35/100
Research direction
Start with the linked diff specification and compare its append/prepend requirements with the array-api-strict behavior shown in the examples. Determine whether Python scalars and 0d arrays should be permitted, then align the specification and implementation with matching tests; the issue names no implementation files or tests.
Written by the indexing model from the issue text.
Description
The specification of diff requires append and prepend to be arrays with the same shape as the first argument except along axis.
array-api-strict currently does not:
import array_api_strict as xp
xp.diff(xp.ones((2, 3)), append=xp.asarray(10), axis=0)
# Array([[0., 0., 0.],
# [9., 9., 9.]], dtype=array_api_strict.float64)
xp.diff(xp.ones((2, 3)), append=xp.asarray(10), axis=1)
# Array([[0., 0., 9.],
# [0., 0., 9.]], dtype=array_api_strict.float64)
Like NumPy, CuPy, and JAX, it expands the value as necessary (and follows the same promotion rules as other functions. I see that following the usual promotion rules was already tabled, so I won't bring that up again right now.)
This suggest that the operation can be well-defined, and I think it can be useful (e.g. prepend 0 and append shape[axis]). It would be even more useful to accept Python scalars, following the example of clip (which also requires array min/max to have the same type as x, but allows Python scalars). This would avoid requiring the user to do something like:
append = xp.full(x.shape[:axis] + (1,) + x.shape[axis:], append, dtype=xp.result_type(x, prepend, append))
- Dominant language
- Python
- Stars
- 281
- Forks
- 52
- PR merge metrics
- No merged PRs in 30d
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