Make behaviour of compute consistent for slicing #419
Merged
Add this suggestion to a batch that can be applied as a single commit.
This suggestion is invalid because no changes were made to the code.
Suggestions cannot be applied while the pull request is closed.
Suggestions cannot be applied while viewing a subset of changes.
Only one suggestion per line can be applied in a batch.
Add this suggestion to a batch that can be applied as a single commit.
Applying suggestions on deleted lines is not supported.
You must change the existing code in this line in order to create a valid suggestion.
Outdated suggestions cannot be applied.
This suggestion has been applied or marked resolved.
Suggestions cannot be applied from pending reviews.
Suggestions cannot be applied on multi-line comments.
Suggestions cannot be applied while the pull request is queued to merge.
Suggestion cannot be applied right now. Please check back later.
As discussed in #399, there were problems for slicing lazy expressions with one where condition, since the output is in general of a different length to the input.
The .compute function when provided with a slice argument internally takes slices of the operands prior to evaluating the expression. One could change this, but I think it is better to interpret the argument as slicing operands prior to calculation. If one is interested in a general slice of the full result one can always force via expr.compute().slice(sl).
An unfortunate consequence is that the syntax of the get_item method is a little misleading (hence why I have changed the tests).
expr.compute(sl)[:] is equal to the numpy syntax nsa1[sl][ne_evaluate(expr)[sl]].