Thanks for taking the time to reply! I appreciate your 2c. I guess my confusion about pure I/O stems from the documentation of phrase_from_file/2 in SWI-Prolog

Thanks for taking the time to reply! I appreciate your 2c. I guess my confusion about pure I/O stems from the documentation of phrase_from_file/2 in SWI-Prolog. The documentation says the predicate is for pure I/O and how it was implemented, and by whom, but it doesn't say what pure I/O is, and why it is needed. I guess the information is somewhere in one (or more) of the canonical Prolog textbooks, which I've only read several years ago (though multiple times over, each). I have to confess also I'm not much of a purist. My Prolog code looks like bog standard imperative code where I feel it doesn't really matter (e.g. I don't have any prejudice about setof/3 or maplist/2 over findall/3), and I guess file I/O is one of those cases. Anyway, thanks again, for your links and explanation. I owe you a quantum of knowledge :)