Sweep highlights holes in Prolog buffer by default so you can easily identify missing terms.
Whether to highlight holes in Sweep Prolog mode buffers with a
dedicated face. By default, this is set to
When the user option
sweeprolog-highlight-holes is set to
nil, Sweep highlights holes in Prolog buffers with a
dedicated face to make them easily distinguishable from regular Prolog
variables. Hole highlighting is enabled by default, to disable it