Flipsign

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

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( -3.14, 10.0 );
// returns -3.14

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

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

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

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, else 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 double-precision floating-point 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 );
}