arf (12/01/82)
I know of four Prolog interpreters running under UNIX, three of which are written in C. I found the previously mentioned PDP 11 assembly language implementation pretty sparse. I particularly objected to its lack of integration into the UNIX environment. It was a real pain to move back and forth between Prolog and an editor. Claude Sammut, from the Univ. of New South Wales, has written a compact interpreter that behaves much like DEC 10 Prolog, but knows enough about UNIX to make the interaction reasonably smooth. He calls his program UNSW Prolog; it has been running for over a year serving students, so it is fairly robust. Fernando Periera, now at SRI, has written CProlog, another attempt to bring DEC 10 Prolog to UNIX. This implementation is still under development, but a preliminary version has been released. It relies on virtual memory support. My biggest gripes with Prolog are its poor programming environment and its lack of support for libraries of programs. I have written, yet another, Prolog interpreter with the primary goals of working well with UNIX and supporting modularity. In summary, if you want a solid Prolog now, I'd suggest using UNSW. Fortunately, Claude is visiting the US and can be reached at `eagle!claude'. Alan Feuer (BTL MH, eagle!arf)