# Identity Function

Evaluate the identity function of a double-precision floating-point number.

The identity-function is defined as

for all x.

## Usage

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


#### identity( x )

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

var v = identity( -1.0 );
// returns -1.0

v = identity( 2.0 );
// returns 2.0

v = identity( 0.0 );
// returns 0.0

v = identity( -0.0 );
// returns -0.0

v = identity( NaN );
// returns NaN


## Examples

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

var rand;
var i;

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


## C APIs

### Usage

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


#### stdlib_base_identity( x )

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

double y = stdlib_base_identity( 2.0 );
// returns 2.0


The function accepts the following arguments:

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


### Examples

#include "stdlib/math/base/special/identity.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_identity( x[ i ] );
printf( "f(%lf) = %lf\n", x[ i ], y );
}
}