Questions from a Fortran HPC Webinar

[ivanpribec]

@Dauptain

A3 - What about newer C++ features (constexpr, auto, modules) and the ISO_C_BINDING? Of course the Fortran binding is for C, but it is often interchangeably used and I wonder if there are plans to support CPP. Essentially at the moment using ISO_C_BINDING seems to restrict both the Fortran features and C(++) features which are usable. How do you see this being resolved?

I am aware of two projects which are somewhat able to close the gap between C++ and Fortran: shroud and swig-fortran (also see this presentation or the arXiv paper). The book Scientific Software Design by Damian @rouson contains a great description of the challenges involved in interfacing C++ and Fortran. Another approach is transpilation like in the upcoming LFortran compiler, but I guess this will only be an option for C++ codes calling Fortran subprograms.

Edit: I just remembered we had a thread open for Automatic Fortran to C++ conversion with a program called fable. The other way round (C++ to Fortran) is more difficult due to the complexity of the C++ type system.

@Dauptain

A5 - Are you aware of any efforts to build a C++ container interface to Fortran arrays using whats available in the “ISO_Fortran_binding.h” header? This would be great to enhance interoperability with C++.

This was my question. Some attempts at this can be found in the stdlib issue #325 originally opened in response to my Discourse thread. I’d be extremely happy if any skilled C++ developers could comment or offer their help in the stdlib issue.