Why would this be down voted? It's a legit question, and a followup in the comment chain.

I understand why SWIG needs a .i file, as it doesn't understand much about the code. But when you control the compiler you can 1> as in the example I gave, look at actual explicit instantiation instead of doing the synthetic thing SWIG does, as well as make other, smarter decisions and 2> use #pragmas or attributes to direct translation at the point of use.

And the author even said himself that "code two files is a pain."

Thus my question remains: why the need for a .clif file?