Direct calls between languages is always going to have some friction because languages have their own data types and cultures, it's unavoidable, but I think man

Direct calls between languages is always going to have some friction because languages have their own data types and cultures, it's unavoidable, but I think many of those systems make it work as well as can be reasonably expected. Meanwhile you have the option of specifying a language neutral protocol for invoking public interfaces across languages, or reuse a wire protocol. Not many people seem to make this tradeoff though, it would usually be a bigger pain than to live with the limitations of cross language direct calls.