{{alias}}( x )
    Evaluates the signum function for a double-precision floating-point number.

    Value | Sign
    ----- | -----
    x > 0 |    +1
    x < 0 |    -1
        0 |     0
       -0 |    -0
      NaN |   NaN

    Parameters
    ----------
    x: number
        Input value.

    Returns
    -------
    sign: number
        Function value.

    Examples
    --------
    > var sign = {{alias}}( -5.0 )
    -1.0
    > sign = {{alias}}( 5.0 )
    1.0
    > sign = {{alias}}( -0.0 )
    -0.0
    > sign = {{alias}}( 0.0 )
    0.0
    > sign = {{alias}}( NaN )
    NaN

    See Also
    --------