Java has Scala and .NET has F#. Both of these languages are very highly integrated into the respective Java and .NET platforms. Classes can be written in Scala then extended i
As has been said, I'm not really sure about a C++ 'ecosystem'. But Haskell does have a Foreign Function Interface that allows you to call C functions from Haskell and Haskell functions from C.
Then again, that's C, I'm not really sure how far along the C++ FFI is...