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# negaLucasf

> Compute the nth [negaLucas number][lucas-number] in single-precision floating-point format.

<section class="intro">

The [negaLucas numbers][lucas-number] are the integer sequence

<!-- <equation class="equation" label="eq:negalucasf_sequence" align="center" raw="2, -1, 3, -4, 7, -11, 18, -29, 47, -76, 123, -199, 322, \ldots" alt="NegaLucas sequence"> -->

<div class="equation" align="center" data-raw-text="2, -1, 3, -4, 7, -11, 18, -29, 47, -76, 123, -199, 322, \ldots" data-equation="eq:negalucasf_sequence">
    <img src="https://cdn.jsdelivr.net/gh/stdlib-js/stdlib@bb29798906e119fcb2af99e94b60407a270c9b32/lib/node_modules/@stdlib/math/base/special/negalucasf/docs/img/equation_negalucas_sequence.svg" alt="NegaLucas sequence">
    <br>
</div> -->

<!-- </equation> -->

The sequence is defined by the recurrence relation

<!-- <equation class="equation" label="eq:negalucasf_recurrence_relation" align="center" raw="L_{n-2} = L_{n} - L_{n-1}" alt="NegaLucas sequence recurrence relation"> -->

<!-- <div class="equation" align="center" data-raw-text="L_{n-2} = L_{n} - L_{n-1}" data-equation="eq:negalucasf_recurrence_relation">
    <img src="https://cdn.jsdelivr.net/gh/stdlib-js/stdlib@bb29798906e119fcb2af99e94b60407a270c9b32/lib/node_modules/@stdlib/math/base/special/negalucasf/docs/img/equation_negalucas_recurrence_relation.svg" alt="NegaLucas sequence recurrence relation">
    <br>
</div> -->

<!-- </equation> -->

which yields

<!-- <equation class="equation" label="eq:negalucasf_lucas" align="center" raw="L_{-n} = (-1)^{n} L_n" alt="NegaLucas relationship to Lucas numbers"> -->

<!-- <div class="equation" align="center" data-raw-text="L_{-n} = (-1)^{n} L_n" data-equation="eq:negalucasf_lucas">
    <img src="https://cdn.jsdelivr.net/gh/stdlib-js/stdlib@bb29798906e119fcb2af99e94b60407a270c9b32/lib/node_modules/@stdlib/math/base/special/negalucasf/docs/img/equation_negalucas_lucas.svg" alt="NegaLucas relationship to Lucas numbers">
    <br>
</div>

<!-- </equation> -->

with seed values `L_0 = 2` and `L_{-1} = -1`.

</section>

<!-- /.intro -->

<section class="usage">

## Usage

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

#### negalucasf( n )

Computes the nth [negaLucas number][lucas-number] in single-precision floating-point format.

```javascript
var v = negalucasf( 0 );
// returns 2

v = negalucasf( -1 );
// returns -1

v = negalucasf( -2 );
// returns 3

v = negalucasf( -3 );
// returns -4

v = negalucasf( -34 );
// returns 12752043
```

If `n < -34`, the function returns `NaN`, as larger [negaLucas numbers][lucas-number] cannot be safely represented in [single-precision floating-point format][ieee754].

```javascript
var v = negalucasf( -35 );
// returns NaN
```

If not provided a nonpositive integer value, the function returns `NaN`.

```javascript
var v = negalucasf( -3.14 );
// returns NaN

v = negalucasf( 1 );
// returns NaN
```

If provided `NaN`, the function returns `NaN`.

```javascript
var v = negalucasf( NaN );
// returns NaN
```

</section>

<!-- /.usage -->

<section class="notes">

</section>

<!-- /.notes -->

<section class="examples">

## Examples

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

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

var v;
var i;

for ( i = 0; i > -35; i-- ) {
    v = negalucasf( i );
    console.log( v );
}
```

</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/negalucasf.h"
```

#### stdlib_base_negalucasf( n )

Computes the nth [negaLucas number][lucas-number] in single-precision floating-point format.

```c
float out = stdlib_base_negalucasf( 0.0f );
// returns 2.0f

out = stdlib_base_negalucasf( -1.0f );
// returns -1.0f
```

The function accepts the following arguments:

-   **n**: `[in] float` input value.

```c
float stdlib_base_negalucasf( const float 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/negalucasf.h"
#include <stdio.h>

int main( void ) {
    float i;
    float v;

    for ( i = 0.0f; i > -35.0f; i-- ) {
        v = stdlib_base_negalucasf( i );
        printf( "negalucasf(%f) = %f\n", i, v );
    }
}
```

</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">

[lucas-number]: https://en.wikipedia.org/wiki/Lucas_number

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

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

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

</section>

<!-- /.links -->
