Macro cgmath::relative_eq

macro_rules! relative_eq {
    ($ lhs : expr, $ rhs : expr $ (, $ opt : ident = $ val : expr) *) => { ... };
    ($ lhs : expr, $ rhs : expr $ (, $ opt : ident = $ val : expr) *,) => { ... };
}

Approximate equality using both the absolute difference and relative based comparisons.