# Flipsign
> Return a complex number with the same magnitude as `z` and the sign of `y*z`.
## Usage
```javascript
var cflipsign = require( '@stdlib/math/base/special/cflipsign' );
```
#### cflipsign( \[out,] re, im, y )
Returns a complex number with the same magnitude as `z` and the sign of `y*z`.
```javascript
var v = cflipsign( -4.2, 5.5, -4 );
// returns [ 4.2, -5.5 ]
v = cflipsign( 0.0, 0.0, 5 );
// returns [ 0.0, 0.0 ]
v = cflipsign( NaN, NaN, 6 );
// returns [ NaN, NaN ]
```
By default, the function returns real and imaginary components as a two-element `array`. To avoid unnecessary memory allocation, the function supports providing an output (destination) object.
```javascript
var Float64Array = require( '@stdlib/array/float64' );
var out = new Float64Array( 2 );
var v = cflipsign( out, -4.2, 5.5, 77 );
// returns [ -4.2, 5.5 ]
var bool = ( v === out );
// returns true
```
## Examples
```javascript
var Complex128 = require( '@stdlib/complex/float64' );
var randu = require( '@stdlib/random/base/randu' );
var real = require( '@stdlib/complex/real' );
var imag = require( '@stdlib/complex/imag' );
var cflipsign = require( '@stdlib/math/base/special/cflipsign' );
var re;
var im;
var z;
var o;
var w;
var i;
var y;
for ( i = 0; i < 100; i++ ) {
re = ( randu()*100.0 ) - 50.0;
im = ( randu()*100.0 ) - 50.0;
y = ( randu()*100.0 ) - 50.0;
z = new Complex128( re, im );
o = cflipsign( real(z), imag(z), y );
w = new Complex128( o[ 0 ], o[ 1 ] );
console.log( 'flipsign(%s) = %s', z.toString(), w.toString() );
}
```