feat: add ndarray/base/find

[headlessNode]

Progresses #2656 .

Description

What is the purpose of this pull request?

This pull request:

• add ndarray/base/find

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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No.

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• Read, understood, and followed the contributing guidelines.

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[stdlib-bot]

Coverage Report

Package	Statements	Branches	Functions	Lines
ndarray/base/find	$\color{red}2118/2205$ $\color{green}+96.05\%$	$\color{red}140/142$ $\color{green}+98.59\%$	$\color{red}13/15$ $\color{green}+86.67\%$	$\color{red}2118/2205$ $\color{green}+96.05\%$

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

[headlessNode]

@kgryte Ready for initial review.

[kgryte]

I suggest switching the order of when x and sentinelValue are defined.

[kgryte]

Suggested change

	- **arrays**: array-like object containing an input ndarray and a zero-dimensional sentinel value ndarray.
	- **arrays**: array-like object containing an input ndarray and a zero-dimensional ndarray containing a sentinel value which should be returned when no element in an input ndarray passes a test implemented by the predicate function.

[kgryte]

Suggested change

	Returns the first element in an ndarray which pass a test implemented by a predicate function.
	Returns the first element in an ndarray which passes a test implemented by a predicate function.

[kgryte]

Suggested change

	> Return the first element in an ndarray which pass a test implemented by a predicate function.
	> Return the first element in an ndarray which passes a test implemented by a predicate function.

Applies here and everywhere.

[kgryte]

Suggested change

	function clbk( value ) {
	function isEven( value ) {

I'd rename to a literate name at least here in the README and other end-user facing documentation.

[kgryte]

Suggested change

	x = discreteUniform( len, 1, 100 );
	x = discreteUniform( len, 1, 100, {
	'dtype': xtype
	});

[kgryte]

I suggest using array/filled. E.g., filledarray( NaN, 1, xtype ); <= check signature, but this should provide the idea. TL;DR: your data buffer array instance should match the xtype, so you need to create a single-element array containing a sentinel value.