SWI Prolog has possibly the most loudly passive-aggressive debugger I've ever seen
The rest of the REPL is just about as passive-aggressive, but not quite as loud.
no, I don't know why you can dynamically assert facts but not rules.
It kind of defeats the whole point of having a REPL at all.
This kind of silliness is why Prolog doesn't quite cut it for interactive exploratory programming.
That was just to test this somewhat baffling line:
http://www.vldb.org/conf/1986/P033.PDF
I don't know in what system this paragraph is true, but it's manifestly false of SWI Prolog. Negation by failure works fine; the line that's supposed to have no definition, returns results.
This bizarreness is just the sort of thing you find when you read 1980s or early-90s logic programming papers.
*shrug*
Maybe the point is that the negation by failure part fails if you run it in *parallel*, which is what most of 80s Prolog / database research was about.
