Macro define_rpc 

macro_rules! define_rpc {
    (
            $publisher:expr,
            $path:expr,
            $topdoc:expr,
            $map:expr,
            $tx:expr,
            $($arg:ident: $typ:ty = $default:expr; $doc:expr),*
        ) => { ... };
    (
            $publisher:expr,
            $flags:expr,
            $path:expr,
            $topdoc:expr,
            $map:expr,
            $tx:expr,
            $($arg:ident: $typ:ty = $default:expr; $doc:expr),*
        ) => { ... };
}

defines a new rpc. define_rpc!(publisher, path, doc, mapfn, tx, arg: typ = default; doc, ...) see Proc for an example