npm package: @stdlib/math-base-special-xlog1py
Description: Compute `x * ln(y+1)` so that the result is `0` if `x = 0`.
Author: The Stdlib Authors
Latest version: 0.3.1

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# xlog1py

[![NPM version][npm-image]][npm-url] [![Build Status][test-image]][test-url] [![Coverage Status][coverage-image]][coverage-url] <!-- [![dependencies][dependencies-image]][dependencies-url] -->

> Compute `x * ln(y+1)` so that the result is `0` if `x = 0`.

<section class="installation">

## Installation

```bash
npm install @stdlib/math-base-special-xlog1py
```

</section>

<section class="usage">

## Usage

```javascript
var xlog1py = require( '@stdlib/math-base-special-xlog1py' );
```

#### xlog1py( x, y )

Computes `x * ln(y+1)` so that the result is `0` if `x = 0`.

```javascript
var out = xlog1py( 3.0, 2.0 );
// returns ~3.296

out = xlog1py( 1.5, 5.9 );
// returns ~2.897

out = xlog1py( 0.9, 1.0 );
// returns ~0.624

out = xlog1py( 1.0, 0.0 );
// returns 0.0

out = xlog1py( 0.0, -2.0 );
// returns 0.0

out = xlog1py( 1.5, NaN );
// returns NaN

out = xlog1py( 0.0, NaN );
// returns NaN

out = xlog1py( NaN, 2.3 );
// returns NaN
```

</section>

<!-- /.usage -->

<section class="examples">

## Examples

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

```javascript
var randu = require( '@stdlib/random-base-randu' );
var xlog1py = require( '@stdlib/math-base-special-xlog1py' );

var x;
var y;
var i;

for ( i = 0; i < 100; i++ ) {
    x = randu();
    if ( x < 0.5 ) {
        x = 0.0;
    }
    y = ( randu() * 20.0 ) - 5.0;
    console.log( 'xlog1py(%d, %d) = %d', x, y, xlog1py( x, y ) );
}
```

</section>

<!-- /.examples -->

<!-- C interface documentation. -->

* * *

<section class="c">

## C APIs

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<section class="intro">

</section>

<!-- /.intro -->

<!-- C usage documentation. -->

<section class="usage">

### Usage

```c
#include "stdlib/math/base/special/xlog1py.h"
```

#### stdlib_base_xlog1py( x, y )

Computes `x * ln(y+1)` so that the result is `0` if `x = 0`.

```c
double v = stdlib_base_xlog1py( 3.0, 2.0 );
// returns ~3.296
```

The function accepts the following arguments:

-   **x**: `[in] double` input value.
-   **y**: `[in] double` input value.

```c
double stdlib_base_xlog1py( const double x, const double y );
```

</section>

<!-- /.usage -->

<!-- C API usage notes. Make sure to keep an empty line after the `section` element and another before the `/section` close. -->

<section class="notes">

</section>

<!-- /.notes -->

<!-- C API usage examples. -->

<section class="examples">

### Examples

```c
#include "stdlib/math/base/special/xlog1py.h"
#include <stdio.h>
#include <stdlib.h>

int main( void ) {
    double out;
    double x;
    double y;
    int i;

    for ( i = 0; i < 100; i++ ) {
        x = ( (double)rand() / (double)RAND_MAX ) * 100.0;
        y = ( (double)rand() / (double)RAND_MAX ) * 5.0;
        out = stdlib_base_xlog1py( x, y );
        printf( "xlog1py(%lf, %lf) = %lf\n", x, y, out );
    }
}
```

</section>

<!-- /.examples -->

</section>

<!-- /.c -->

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

<section class="related">

* * *

## See Also

-   <span class="package-name">[`@stdlib/math-base/special/log1p`][@stdlib/math/base/special/log1p]</span><span class="delimiter">: </span><span class="description">evaluate the natural logarithm of 1+x.</span>
-   <span class="package-name">[`@stdlib/math-base/special/xlogy`][@stdlib/math/base/special/xlogy]</span><span class="delimiter">: </span><span class="description">compute `x * ln(y)` so that the result is `0` if `x = 0`.</span>

</section>

<!-- /.related -->

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<section class="main-repo" >

* * *

## Notice

This package is part of [stdlib][stdlib], a standard library for JavaScript and Node.js, with an emphasis on numerical and scientific computing. The library provides a collection of robust, high performance libraries for mathematics, statistics, streams, utilities, and more.

For more information on the project, filing bug reports and feature requests, and guidance on how to develop [stdlib][stdlib], see the main project [repository][stdlib].

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---

## License

See [LICENSE][stdlib-license].


## Copyright

Copyright &copy; 2016-2026. The Stdlib [Authors][stdlib-authors].

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[@stdlib/math/base/special/log1p]: https://www.npmjs.com/package/@stdlib/math-base-special-log1p

[@stdlib/math/base/special/xlogy]: https://www.npmjs.com/package/@stdlib/math-base-special-xlogy

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</section>

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