[RFC]: add `@stdlib/iter/cuany-by`

[kgryte]

Description

This RFC proposes adding the package @stdlib/iter/cuany-by, which cumulatively tests whether at least one iterated value passes a test implemented by a predicate function. The returned iterator should be a transform iterator, continuing to iterate while source iterator values are available.

var array2iterator = require( '@stdlib/array/to-iterator' );

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

var arr = array2iterator( [ 0, 0, 0, 1, 0 ] );

var it = iterCuAnyBy( arr, isPositive );

var v = it.next().value;
// returns false

v = it.next().value;
// returns false

v = it.next().value;
// returns false

v = it.next().value;
// returns true

v = it.next().value;
// returns true

var bool = it.next().done;
// returns true

The predicate function should be provided two arguments:

• value: the iterated value.
• index: iteration index (zero-based).

Related Issues

No.

Questions

No.

Other

• See also @stdlib/iter/any-by

Checklist

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

[pra2107tham]

Hii, I would like to start my open source contribution by solving this issue. Can anyone assign me to it?

[kgryte]

@pra2107tham Thanks for volunteering to work on this. Please feel free to submit a PR implementing this feature.

[pra2107tham]

Can you please tell me step by step way of solving this issue. i am not getting on how to do it?

[kgryte]

@pra2107tham I suggest copying the package iter/cuany to iter/cuany-by and then refactoring to support a callback argument. The signature of the main export should match iter/any-by, but the behavior should be similar to cuany.

[pra2107tham]

Where is the predicate function in the code? i am not able to find it?

[kgryte]

There isn't a predicate function in iter/cuany. The purpose of this RFC is to create a separate package exposing a transform iterator which is similiar to cuany but provides an implementation supporting a predicate function. An example of a sink iterator which supports a predicate function is any-by. To implement this package, you need to borrow the interface of any-by and extend the behavior of cuany.