feat: add blas/ext/last-index-of

[headlessNode]

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Progreses #2656.

Description

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This pull request:

• add blas/ext/last-index-of

Related Issues

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This pull request:

• progresses [RFC]: achieve ndarray API parity with built-in JavaScript arrays  #2656

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• Read, understood, and followed the contributing guidelines.

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[stdlib-bot]

Coverage Report

Package	Statements	Branches	Functions	Lines
blas/ext/last-index-of	$\color{red}656/666$ $\color{green}+98.50\%$	$\color{red}74/78$ $\color{green}+94.87\%$	$\color{green}3/3$ $\color{green}+100.00\%$	$\color{red}656/666$ $\color{green}+98.50\%$

The above coverage report was generated for the changes in this PR.

[kgryte]

@headlessNode You'll want to make similar changes as done in #7565 in this PR.

[headlessNode]

@kgryte done

[kgryte]

I don't think this is the test that you want. You have already tested "broadcasting" of a scalar from index above. Here, you are testing that broadcasting works when specifying a dimension. That is fine, but also does not cover the case where fromIndex is an ndarray which is NOT broadcasted. Here, that would be fromIndex is a two-element vector, which would test the case where we use a different from index value for the two columns.

You can choose to keep this and the following tests, but you need to update the descriptions, and, at a minimum, you need to add tests for when the from index argument is not broadcasted and using different from indices. You should also test similarly for the search element (i.e., meaning a test where the search element is different for each searched row/column).

[kgryte]

This same comment may be applicable for blas/ext/index-of.

[kgryte]

I think we've initialized the fromIndex incorrectly here, as this doesn't follow https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/lastIndexOf semantics. There, fromIndex specifies the first element at which to begin searching backward. Here, fromIndex is used similar to indexOf and something like a means for reducing the sub-array.

This also needs to be addressed in blas/ext/base/*last-index-of, as, looking at examples, those all don't appear to be parameterized correctly based upon conventional semantics.

[kgryte]

Left an initial review.