Macro tern_py

macro_rules! tern_py {
    ({ $if_expr:expr } if ($cond:expr) else { $else_expr:expr }) => { ... };
}

The same as tern_python macro but shorter:

let y = 4;
let x = tern_py! { { "it's even" } if (y & 1 == 0) else { "it's odd" } };

println!("{} is {}", y, x);