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# csignum

> Evaluate the [signum][signum] function of a double-precision complex floating-point number.

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## Usage

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

#### csignum( z )

Evaluates the [signum][signum] function of a double-precision complex floating-point number.

```javascript
var Complex128 = require( '@stdlib/complex/float64/ctor' );

var v = csignum( new Complex128( -4.2, 5.5 ) );
// returns <Complex128>[ -0.6069136033622302, 0.79476781392673 ]

v = csignum( new Complex128( 0.0, 0.0 ) );
// returns <Complex128>[ 0.0, 0.0 ]

v = csignum( new Complex128( NaN, NaN ) );
// returns <Complex128>[ NaN, NaN ]
```

</section>

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## Examples

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```javascript
var uniform = require( '@stdlib/random/base/uniform' ).factory;
var Complex128 = require( '@stdlib/complex/float64/ctor' );
var csignum = require( '@stdlib/math/base/special/csignum' );

var rand = uniform( -50.0, 50.0 );

var z;
var i;
for ( i = 0; i < 100; i++ ) {
    z = new Complex128( rand(), rand() );
    console.log( 'csignum(%s) = %s', z, csignum( z ) );
}
```

</section>

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* * *

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## C APIs

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### Usage

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

#### stdlib_base_csignum( z )

Evaluates the [signum][signum] function of a double-precision complex floating-point number.

```c
#include "stdlib/complex/float64/ctor.h"
#include "stdlib/complex/float64/real.h"
#include "stdlib/complex/float64/imag.h"

stdlib_complex128_t z = stdlib_complex128( -4.2, 5.5 );

stdlib_complex128_t out = stdlib_base_csignum( z );

double re = stdlib_complex128_real( out );
// returns -0.6069136033622302

double im = stdlib_complex128_imag( out );
// returns 0.79476781392673
```

The function accepts the following arguments:

-   **z**: `[in] stdlib_complex128_t` input value.

```c
stdlib_complex128_t stdlib_base_csignum( const stdlib_complex128_t z );
```

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### Examples

```c
#include "stdlib/math/base/special/csignum.h"
#include "stdlib/complex/float64/ctor.h"
#include "stdlib/complex/float64/reim.h"
#include <stdio.h>

int main( void ) {
    const stdlib_complex128_t x[] = {
        stdlib_complex128( 3.14, 1.5 ),
        stdlib_complex128( -3.14, -1.5 ),
        stdlib_complex128( 0.0, 0.0 ),
        stdlib_complex128( 0.0/0.0, 0.0/0.0 )
    };

    stdlib_complex128_t v;
    stdlib_complex128_t y;
    double re1;
    double im1;
    double re2;
    double im2;
    int i;
    for ( i = 0; i < 4; i++ ) {
        v = x[ i ];
        y = stdlib_base_csignum( v );
        stdlib_complex128_reim( v, &re1, &im1 );
        stdlib_complex128_reim( y, &re2, &im2 );
        printf( "csignum(%lf + %lfi) = %lf + %lfi\n", re1, im1, re2, im2 );
    }
}
```

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</section>

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* * *

## See Also

-   <span class="package-name">[`@stdlib/math/base/special/signum`][@stdlib/math/base/special/signum]</span><span class="delimiter">: </span><span class="description">evaluate the signum function for a double-precision floating-point number.</span>

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[signum]: https://en.wikipedia.org/wiki/Sign_function

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[@stdlib/math/base/special/signum]: https://github.com/stdlib-js/math/tree/main/base/special/signum

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</section>

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