OO capabilities of Fortran 2018 vs c++

[Beliavsky]

@septc

I have no experience with FEM codes so not sure at all, but if they use multiple inheritance (for any purpose), I guess one needs to think some workarounds because it is not supported by Fortran OO.

I posted a paper Emulating Multiple Inheritance in Fortran 2003/2008 but am unqualified to evaluate it, as a Fortranner without CLASS.