# @stdlib/math-base-special-flipsign

0.2.2 • Public • Published

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# flipsign

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

## Installation

npm install @stdlib/math-base-special-flipsign

## Usage

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

#### flipsign( x, y )

Returns a double-precision floating-point number with the magnitude of x and the sign of x*y (i.e., only return -x when y is a negative number).

var z = flipsign( -3.0, 10.0 );
// returns -3.0

z = flipsign( -3.0, -1.0 );
// returns 3.0

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

z = flipsign( -3.0, -0.0 );
// returns 3.0

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

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

## Notes

• According to the IEEE 754 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 flipsign = require( '@stdlib/math-base-special-flipsign' );

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

// Generate random numbers `x` and `y` and flip the sign of `x` only if `y` is negative...
for ( i = 0; i < 100; i++ ) {
x = (randu()*100.0) - 50.0;
y = (randu()*10.0) - 5.0;
z = flipsign( x, y );
console.log( 'x: %d, y: %d => %d', x, y, z );
}

## C APIs

### Usage

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

#### stdlib_base_flipsign( x, y )

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

double v = stdlib_base_flipsign( -3.0, 10.0 );
// returns -3.0

double v = stdlib_base_flipsign( -3.0, -1.0 );
// returns 3.0

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_flipsign( const double x, const double y );

### Examples

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

int main( void ) {
const double x[] = { 3.0, -3.0, 0.0, 0.0/0.0 };

double y;
int i;
for ( i = 0; i < 4; i++ ) {
y = stdlib_base_flipsign( x[ i ], -3.0 );
printf( "flipsign(%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.

## Package Sidebar

### Install

npm i @stdlib/math-base-special-flipsign

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