Function calc_sign 

pub fn calc_sign(value: CSSFloat) -> CSSFloat

Computes the sign of the given value. The CSS Values and Units definition for sign() returns +0 or -0 for an input of +0 or -0, respectively (whereas the Rust f32::signum() function returns +1 or -1, respectively). https://drafts.csswg.org/css-values-4/#funcdef-sign