# npm

## @stdlib/math-base-special-copysign 0.0.7 • Public • Published

# copysign

Return a double-precision floating-point number with the magnitude of `x` and the sign of `y`.

## Installation

`npm install @stdlib/math-base-special-copysign`

## Usage

`var copysign = require( '@stdlib/math-base-special-copysign' );`

#### copysign( x, y )

Returns a double-precision floating-point number with the magnitude of `x` and the sign of `y`.

```var z = copysign( -3.14, 10.0 );
// returns 3.14

z = copysign( 3.14, -1.0 );
// returns -3.14

z = copysign( 1.0, -0.0 );
// returns -1.0

z = copysign( -3.14, -0.0 );
// returns -3.14

z = copysign( -0.0, 1.0 );
// returns 0.0```

## Notes

• According to the IEEE754 standard, a `NaN` has a biased exponent equal to `2047`, a significand greater than `0`, and a sign bit equal to either `1` or `0`. In which case, `NaN` may not correspond to just one but many binary representations. Accordingly, care should be taken to ensure that `y` is not `NaN`; otherwise, behavior may be indeterminate.

## Examples

```var randu = require( '@stdlib/random-base-randu' );
var copysign = require( '@stdlib/math-base-special-copysign' );

var x;
var y;
var z;
var i;

// Generate random double-precision floating-point numbers `x` and `y` and copy the sign of `y` to `x`...
for ( i = 0; i < 100; i++ ) {
x = (randu()*100.0) - 50.0;
y = (randu()*10.0) - 5.0;
z = copysign( x, y );
console.log( 'x: %d, y: %d => %d', x, y, z );
}```

## C APIs

### Usage

`#include "stdlib/math/base/special/copysign.h"`

#### stdlib_base_copysign( x, y )

Returns a double-precision floating-point number with the magnitude of `x` and the sign of `y`.

```double v = stdlib_base_copysign( -3.14, 10.0 );
// returns 3.14

double v = stdlib_base_copysign( 3.14, -1.0 );
// returns -3.14```

The function accepts the following arguments:

• x: `[in] double` number from which to derive a magnitude.
• y: `[in] double` number from which to derive a sign.
`double stdlib_base_copysign( const double x, const double y );`

### Examples

```#include "stdlib/math/base/special/copysign.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_copysign( x[ i ], -3.0 );
printf( "copysign(%lf, %lf) = %lf\n", x[ i ], -3.0, y );
}
}```

## Notice

This package is part of stdlib, a standard library for JavaScript and Node.js, with an emphasis on numerical and scientific computing. The library provides a collection of robust, high performance libraries for mathematics, statistics, streams, utilities, and more.

For more information on the project, filing bug reports and feature requests, and guidance on how to develop stdlib, see the main project repository.

#### Community ### Install

`npm i @stdlib/math-base-special-copysign`

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