[RFC]: add `@stdlib/array/base/cusome-by-right`

[kgryte]

Description

This RFC proposes adding the package @stdlib/array/base/cusome-by-right, which cumulatively tests whether at least n array elements in a provided array pass a test implemented by a predicate function, while iterating from right-to-left. The function should return a new generic array. The package should also provide an #assign API for setting output values in a provided output array.

function isPositive( value ) {
	return ( value > 0 );
}

var x = [ 1, 1, 0, 0, 0 ];

var y1 = cusomeByRight( x, 2, isPositive );
// returns [ false, false, false, false, true ]

var y2 = [ false, null, false, null, false, null, false, null, false, null ];
var out = cusomeByRight.assign( x, 2, y2, 2, 0, isPositive );
// returns [ false, null, false, null, false, null, false, null, true, null ]

var bool = ( out === y2 );
// returns true

where the assign API supports an offset and stride (see, e.g., @stdlib/array/base/take). Note that, by iterating from right to left, the values in the output array are equivalent to having first reversed the input array x and then using left-to-right iteration.

Both APIs should support accessor arrays (see, e.g., @stdlib/array/base/take).

Related Issues

No.

Questions

No.

Other

• See also @stdlib/utils/some-by-right

Checklist

• [X] I have read and understood the Code of Conduct.
• [X] Searched for existing issues and pull requests.
• [X] The issue name begins with RFC:.

[BarryByte]

@kgryte May i work on this issue ? It is labelled as good first issue, it might help me to start contributing to this organization.

[AbhinavKRN]

@kgryte Can you assign this issue to me?

[srivastavaarpit977]

Hey @kgryte I want to work on this issue.....plz assign this issue to me !!

[stdlib-bot]

:rotating_light: Important: PLEASE READ :rotating_light:

This issue has been labeled as a good first issue and is available for anyone to work on.

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:sparkles: Thank you again for your interest in stdlib, and we look forward to reviewing your future contriubtions. :sparkles:

[GittyHarsha]

Hi, is it expected to use @stdlib/utils/some-by-right to implement @stdlib/array/base/cusome-by-right ? If so, doesn’t this approach result in quadratic time complexity?

[kgryte]

@GittyHarsha No, you should not use @stdlib/utils/some-by-right to implement the proposed API. The implementation should be similar to other similar packages in @stdlib/array/base.

[GittyHarsha]

Hi, I got a doubt while implementing the #assign API. In reference to @stdlib/array/base/take/lib/assign.js, the accessor arrays of type complex and boolean are explicitly handled. I think for @stdlib/array/base/cusome-by-right, there is no need to explicitly handle any types of accessor arrays?

[kgryte]

@GittyHarsha You do need to handle accessor arrays; however, I think you are right that you don't need to special case either ComplexXXArrays or BooleanArray.

E.g., in https://github.com/stdlib-js/stdlib/blob/develop/lib/node_modules/%40stdlib/array/base/cuany/lib/assign.js, we special case complex and boolean arrays, with a fallback to a general accessor utility. For your case, I think you only need the general accessor utility.