function copysignf( x, y ) {
	var wx;
	var wy;

	x = float64ToFloat32( x );
	y = float64ToFloat32( y );

	// Convert `x` to an unsigned integer:
	wx = toWord( x );

	// Turn off the sign bit of `x`:
	wx &= ABS_MASK;

	// Convert `y` to an unsigned integer:
	wy = toWord( y );

	// Leave only the sign bit of `y` turned on:
	wy &= SIGN_MASK;

	// Copy the sign bit of `y` to `x`:
	wx |= wy;

	// Return a new value having the same magnitude as `x`, but with the sign of `y`:
	return fromWord( wx );
}
Returns a single-precision floating-point number with the magnitude of `x` and the sign of `y`.

@param {number} x - number from which to derive a magnitude
@param {number} y - number from which to derive a sign
@returns {number} a single-precision floating-point number

@example
var z = copysignf( -3.0, 10.0 );
// returns 3.0

@example
var z = copysignf( 3.0, -1.0 );
// returns -3.0

@example
var z = copysignf( 1.0, -0.0 );
// returns -1.0

@example
var z = copysignf( -3.0, -0.0 );
// returns -3.0

@example
var z = copysignf( -0.0, 1.0 );
// returns 0.0