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

[kgryte]

Description

This RFC proposes adding the package @stdlib/iter/cunone-by, which cumulatively tests whether no 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 = iterCuNoneBy( arr, isPositive );

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

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

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

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

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

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/none-by

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:.

[Ad11xx]

Hi @kgryte , can I solve this?

[kgryte]

@Ad11xx Thanks for volunteering to work on this. Please feel free to submit a PR implementing this feature.

[Ad11xx]

Thanks a lot! if it is possible is there any file I can refer to regarding the code practices?

[kgryte]

Yes, you should look at both @stdlib/iter/none-by (which is a sink iterator) and @stdlib/iter/for-each, which is a transform iterator. The package you are planning to add should be a combination of the two.

[stdlib-bot]

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[chiru200513]

i would like to start working on this feature . is there anyone currently working on it or can i start ? And also how about the below code? function iterCuNoneBy(iterator, predicate) { let cumulative = true; // Start assuming that no elements satisfy the predicate

return {
    next: function() {
        const next = iterator.next();
        if (next.done) {
            return { value: undefined, done: true };
        }

        // If any element satisfies the predicate, cumulative becomes false
        if (cumulative && predicate(next.value)) {
            cumulative = false;
        }

        return { value: cumulative, done: false };
    }
};

}

module.exports = iterCuNoneBy;