# Signum

Signum function.

The signum function is defined as

for any real number x.

## Usage

var signum = require( '@stdlib/math/base/special/signum' );


#### signum( x )

Evaluates the signum function for a double-precision floating-point number.

var sign = signum( -5.0 );
// returns -1

sign = signum( 5.0 );
// returns 1

sign = signum( -0.0 );
// returns -0

sign = signum( 0.0 );
// returns 0

sign = signum( NaN );
// returns NaN


## Notes

Table of results:

ValueSign
x > 0+1
x < 0-1
00
-0-0
NaNNaN

## Examples

var randu = require( '@stdlib/random/base/randu' );
var round = require( '@stdlib/math/base/special/round' );
var signum = require( '@stdlib/math/base/special/signum' );

var sign;
var x;
var i;

for ( i = 0; i < 100; i++ ) {
x = round( randu()*100.0 ) - 50.0;
sign = signum( x );
console.log( 'signum(%d) = %d', x, sign );
}


## C APIs

### Usage

#include "stdlib/math/base/special/signum.h"


#### stdlib_base_signum( x )

Evaluates the signum function for a double-precision floating-point number.

double y = stdlib_base_signum( -9.0 );
// returns -1.0


The function accepts the following arguments:

• x: [in] double input value.
double stdlib_base_signum( const double x );


### Examples

#include "stdlib/math/base/special/signum.h"
#include <stdio.h>

int main() {
double x[] = { 3.14, -3.14, 0.0, 0.0/0.0 };

double y;
int i;
for ( i = 0; i < 4; i++ ) {
y = stdlib_base_signum( x[ i ] );
printf( "signum(%lf) = %lf\n", x[ i ], y );
}
}