function signumf( x ) {
	if ( x === 0.0 || isnanf( x ) ) {
		return x; // addresses both +-0
	}
	return ( x < 0.0 ) ? -1.0 : 1.0;
}
Evaluates the signum function for a single-precision floating-point number.

@param {number} x - input value
@returns {number} function value

@example
var sign = signumf( -5.0 );
// returns -1.0

@example
var sign = signumf( 5.0 );
// returns 1.0

@example
var sign = signumf( -0.0 );
// returns -0.0

@example
var sign = signumf( 0.0 );
// returns 0.0

@example
var sign = signumf( NaN );
// returns NaN