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# roundnf

> Round a single-precision floating-point number to the nearest multiple of 10^n.

<section class="usage">

## Usage

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

#### roundnf( x, n )

Rounds a single-precision floating-point number to the nearest multiple of `10^n`.

```javascript
// Round a value to 2 decimal places:
var v = roundnf( 3.1415927410125732, -2 );
// returns ~3.14

// If n = 0, `roundnf` behaves like `roundf`:
v = roundnf( 3.1415927410125732, 0 );
// returns 3.0

// Round a value to the nearest thousand:
v = roundnf( 12368.0, 3 );
// returns ~12000.0
```

</section>

<!-- /.usage -->

<section class="notes">

## Notes

-   When operating on [floating-point numbers][ieee754] in bases other than `2`, rounding to specified digits can be **inexact**. For example,

    ```javascript
    var x = 0.2 + 0.1;
    // returns 0.30000000000000004

    // Should round to 0.3...
    var v = roundnf( x, -7 );
    // returns 0.30000001192092896
    ```

-   Ties are rounded toward positive infinity.

</section>

<!-- /.notes -->

<section class="examples">

## Examples

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

```javascript
var discreteUniform = require( '@stdlib/random/array/discrete-uniform' );
var uniform = require( '@stdlib/random/array/uniform' );
var logEachMap = require( '@stdlib/console/log-each-map' );
var roundnf = require( '@stdlib/math/base/special/roundnf' );

var x = uniform( 100, -50.0, 50.0, {
    'dtype': 'float32'
});

var n = discreteUniform( 100, -5, 0, {
    'dtype': 'int32'
});

logEachMap( 'x: %0.8f. Number of decimals: %d. Rounded: %0.8f.', x, n, roundnf );
```

</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/roundnf.h"
```

#### stdlib_base_roundnf( x, n )

Rounds a single-precision floating-point number to the nearest multiple of `10^n`.

```c
// Round a value to 2 decimal places:
float y = stdlib_base_roundnf( 3.14159f, -2 );
// returns ~3.14f

// If n = 0, `roundnf` behaves like `roundf`:
y = stdlib_base_roundnf( 3.14159f, 0 );
// returns 3.0f
```

The function accepts the following arguments:

-   **x**: `[in] float` input value.
-   **n**: `[in] int32_t` integer power of 10.

```c
float stdlib_base_roundnf( const float x, const int32_t n );
```

</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/roundnf.h"
#include <stdio.h>

int main( void ) {
    const float x[] = { 3.14f, -3.14f, 0.0f, 0.0f/0.0f };

    float y;
    int i;
    for ( i = 0; i < 4; i++ ) {
        y = stdlib_base_roundnf( x[ i ], -2 );
        printf( "roundnf(%f, -2) = %f\n", x[ i ], y );
    }
}
```

</section>

<!-- /.examples -->

</section>

<!-- /.c -->

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

<section class="related">

</section>

<!-- /.related -->

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

<section class="links">

[ieee754]: https://en.wikipedia.org/wiki/IEEE_754-1985

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

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

</section>

<!-- /.links -->
