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Return a doubleprecision floatingpoint number with the magnitude of
x
and the sign ofx*y
.
npm install @stdlib/mathbasespecialflipsign
var flipsign = require( '@stdlib/mathbasespecialflipsign' );
Returns a doubleprecision floatingpoint 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
 According to the IEEE 754 standard, a
NaN
has a biased exponent equal to2047
, a significand greater than0
, and a sign bit equal to either1
or0
. In which case,NaN
may not correspond to just one but many binary representations. Accordingly, care should be taken to ensure thaty
is notNaN
; otherwise, behavior may be indeterminate.
var randu = require( '@stdlib/randombaserandu' );
var flipsign = require( '@stdlib/mathbasespecialflipsign' );
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 );
}
#include "stdlib/math/base/special/flipsign.h"
Returns a doubleprecision floatingpoint 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 );
#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 );
}
}

@stdlib/mathbase/special/copysign
: return a doubleprecision floatingpoint number with the magnitude of x and the sign of y.
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.
See LICENSE.
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