So the Prolog mode that comes with Emacs sucks. Well, here is a better alternative, with all the features you would expect, including syntax highlighting, auto indent, and full interaction with an inferior Prolog process. This mode supports in principle any Prolog system, though it is primarily maintained with SWI Prolog in mind. It also has some special tweaks for SICStus Prolog, and explicitly supports Prolog's close relatives Eclipse and Mercury.
So the Prolog mode that comes with Emacs sucks. Well, here is a better alternative, with all the features you would expect, including syntax highlighting, auto indent, and full interaction with an inferior Prolog process. This mode supports in principle any Prolog system, though it is primarily maintained with SWI Prolog in mind. It also has some special tweaks for SICStus Prolog, and explicitly supports Prolog's close relatives Eclipse and Mercury.
To install prolog-mode.el, run the following command in macOS terminal (Applications->Utilities->Terminal)
sudo port install prolog-mode.el
To see what files were installed by prolog-mode.el, run:
port contents prolog-mode.el
To later upgrade prolog-mode.el, run:
sudo port selfupdate && sudo port upgrade prolog-mode.el
Reporting an issue on MacPorts Trac
The MacPorts Project uses a system called Trac to file tickets to report bugs and enhancement requests.
Though anyone may search Trac for tickets, you must have a GitHub account in order to login to Trac to create tickets.