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# gcusome

> Cumulatively test whether at least `k` elements in a strided array are truthy.

<section class="intro">

</section>

<!-- /.intro -->

<section class="usage">

## Usage

```javascript
var gcusome = require( '@stdlib/blas/ext/base/gcusome' );
```

#### gcusome( N, k, x, strideX, out, strideOut )

Cumulatively tests whether at least `k` elements in a strided array are truthy.

```javascript
var x = [ 0, 0, 1, 1, 1 ];
var out = [ false, false, false, false, false ];

gcusome( x.length, 2, x, 1, out, 1 );
// out => [ false, false, false, true, true ]
```

The function has the following parameters:

-   **N**: number of indexed elements.
-   **k**: minimum number of truthy elements.
-   **x**: input [`Array`][mdn-array] or [`typed array`][mdn-typed-array].
-   **strideX**: stride length for `x`.
-   **out**: output [`Array`][mdn-array] or [`typed array`][mdn-typed-array].
-   **strideOut**: stride length for `out`.

The `N` and stride parameters determine which elements in the strided arrays are accessed at runtime. For example, to cumulatively test every other element:

```javascript
var x = [ 0, 0, 1, 0, 1, 0, 1, 0 ];
var out = [ false, false, false, false ];

gcusome( 4, 2, x, 2, out, 1 );
// out => [ false, false, true, true ]
```

Note that indexing is relative to the first index. To introduce an offset, use [`typed array`][mdn-typed-array] views.

<!-- eslint-disable stdlib/capitalized-comments -->

```javascript
var Uint8Array = require( '@stdlib/array/uint8' );

// Initial arrays...
var x0 = new Uint8Array( [ 0, 0, 1, 0, 1, 1 ] );
var o0 = new Uint8Array( x0.length );

// Create offset views...
var x1 = new Uint8Array( x0.buffer, x0.BYTES_PER_ELEMENT*1 ); // start at 2nd element
var o1 = new Uint8Array( o0.buffer, o0.BYTES_PER_ELEMENT*3 ); // start at 4th element

gcusome( 3, 2, x1, 2, o1, 1 );
// o0 => <Uint8Array>[ 0, 0, 0, 0, 0, 0 ]
```

#### gcusome.ndarray( N, k, x, strideX, offsetX, out, strideOut, offsetOut )

Cumulatively tests whether at least `k` elements in a strided array are truthy using alternative indexing semantics.

```javascript
var x = [ 0, 0, 1, 1, 1 ];
var out = [ false, false, false, false, false ];

gcusome.ndarray( x.length, 2, x, 1, 0, out, 1, 0 );
// out => [ false, false, false, true, true ]
```

The function has the following additional parameters:

-   **offsetX**: starting index for `x`.
-   **offsetOut**: starting index for `out`.

While [`typed array`][mdn-typed-array] views mandate a view offset based on the underlying buffer, offset parameters support indexing semantics based on starting indices. For example, to cumulatively test every other element starting from the third element:

```javascript
var x = [ 0, 0, 1, 0, 1, 0, 1, 0 ];
var out = [ false, false, false ];

gcusome.ndarray( 3, 2, x, 2, 2, out, 1, 0 );
// out => [ false, true, true ]
```

</section>

<!-- /.usage -->

<section class="notes">

## Notes

-   If `N <= 0`, both functions return `out` unchanged.
-   Both functions support array-like objects having getter and setter accessors for array element access (e.g., [`@stdlib/array/base/accessor`][@stdlib/array/base/accessor]).

</section>

<!-- /.notes -->

<section class="examples">

## Examples

<!-- eslint no-undef: "error" -->

```javascript
var bernoulli = require( '@stdlib/random/array/bernoulli' );
var filled = require( '@stdlib/array/base/filled' );
var gcusome = require( '@stdlib/blas/ext/base/gcusome' );

var x = bernoulli( 10, 0.5, {
    'dtype': 'generic'
});
console.log( x );

var out = filled( false, x.length );
gcusome( x.length, 2, x, 1, out, 1 );
console.log( out );
```

</section>

<!-- /.examples -->

<!-- Section for related `stdlib` packages. Do not manually edit this section, as it is automatically populated. -->

<section class="related">

</section>

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<!-- Section for all links. Make sure to keep an empty line after the `section` element and another before the `/section` close. -->

<section class="links">

[mdn-array]: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array

[mdn-typed-array]: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/TypedArray

[@stdlib/array/base/accessor]: https://www.npmjs.com/package/@stdlib/array-base-accessor

<!-- <related-links> -->

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</section>

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