npm package: @stdlib/math-base-special-rempio2f
Description: Compute `x - nπ/2 = r`.
Author: The Stdlib Authors
Latest version: 0.1.1

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# rempio2f

[![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 - nπ/2 = r` (single-precision).

<section class="installation">

## Installation

```bash
npm install @stdlib/math-base-special-rempio2f
```

</section>

<section class="usage">

## Usage

```javascript
var rempio2f = require( '@stdlib/math-base-special-rempio2f' );
```

#### rempio2f( x, y )

Computes `x - nπ/2 = r`.

```javascript
var y = [ 0.0 ];
var n = rempio2f( 128.0, y );
// returns 81

var y1 = y[ 0 ];
// returns ~0.765
```

When `x` is `NaN` or infinite, the function returns `0` and sets `y[0]` to `NaN`.

```javascript
var y = [ 0.0 ];
var n = rempio2f( NaN, y );
// returns 0

var y1 = y[ 0 ];
// returns NaN

y = [ 0.0 ];
n = rempio2f( Infinity, y );
// returns 0

y1 = y[ 0 ];
// returns NaN
```

</section>

<!-- /.usage -->

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

<section class="notes">

## Notes

-   The function returns `n` and stores the remainder `r` as `y[0]`.
-   For input values larger than `2^28*π/2` in magnitude, the function **only** returns the last three binary digits of `n` and not the full result.

</section>

<!-- /.notes -->

<section class="examples">

## Examples

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

```javascript
var linspace = require( '@stdlib/array-base-linspace' );
var rempio2f = require( '@stdlib/math-base-special-rempio2f' );

var x = linspace( 0.0, 100.0, 100 );
var y = [ 0.0 ];
var n;
var i;

for ( i = 0; i < x.length; i++ ) {
    n = rempio2f( x[ i ], y );
    console.log( '%d - %dπ/2 = %d', x[ i ], n, y[ 0 ] );
}
```

</section>

<!-- /.examples -->

<!-- C interface documentation. -->

* * *

<section class="c">

## C APIs

<!-- Section to include introductory text. Make sure to keep an empty line after the intro `section` element and another before the `/section` close. -->

<section class="intro">

</section>

<!-- /.intro -->

<!-- C usage documentation. -->

<section class="usage">

### Usage

```c
#include "stdlib/math/base/special/rempio2f.h"
```

#### stdlib_base_rempio2f( x, &rem )

Computes `x - nπ/2 = r` (single-precision).

```c
#include <stdint.h>

double rem;

int32_t n = stdlib_base_rempio2f( 4.0f, &rem );
```

The function accepts the following arguments:

-   **x**: `[in] float` input value.
-   **rem**: `[out] double*` destination for the remainder.

```c
int32_t stdlib_base_rempio2f( const float x, double *rem );
```

</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/rempio2f.h"
#include <stdio.h>
#include <stdint.h>
#include <inttypes.h>

int main( void ) {
    const float x[] = { 0.0f, 1.0f, 4.0f, 128.0f };

    double rem;
    int32_t n;
    int i;
    for ( i = 0; i < 4; i++ ) {
        n = stdlib_base_rempio2f( x[ i ], &rem );
        printf( "%f - %"PRId32"π/2 = %lf\n", x[ i ], n, rem );
    }
}
```

</section>

<!-- /.examples -->

</section>

<!-- /.c -->

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<section class="related">

</section>

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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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---

## Copyright

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

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