Macro impl_cmp

macro_rules! impl_cmp {
    (
        eq
        $t:ident
        {
            $($code:tt)*
        }
    ) => { ... };
    (
        partial_eq
        $t:ident
        {
            $($code:tt)*
        }
    ) => { ... };
    (
        ord
        $t:ident
        {
            $($code:tt)*
        }
    ) => { ... };
    (
        partial_ord
        $t:ident
        {
            $($code:tt)*
        }
    ) => { ... };
    (
        partial_eq
        $t1:ident, $t2:ident
        {
            $($code:tt)*
        }
    ) => { ... };
    (
        partial_ord
        $t1:ident, $t2:ident
        {
            $($code:tt)*
        }
    ) => { ... };
}

Macros for overloading comparison operators