It appears that either I'm doing something blatantly stupid or #lang racklog documentation misses some points.
Here the question.
According to the documentation
This module language accepts the syntax of Datalog (except clauses need not be safe) and compiles each predicate to a relation.
The accepted syntax is available in the Datalog Module Language documentation.
Then, trying to run the example given in datalog, simply swapping "racklog" in place of "datalog"
#lang racklog
(racket/base). % here the parenthesis are not required, correct is racket/base. I remove those but then...
fib(0, 0). % from here onward, numbers are not recognized
fib(1, 1).
fib(N, F) :- N != 1,
N != 0,
N1 :- -(N, 1),
N2 :- -(N, 2),
fib(N1, F1),
fib(N2, F2),
F :- +(F1, F2).
fib(30, F)?
Specifically, the message of error regarding the first number is
match-lambda: no matching clause for '#s(constant (14-unsaved-editor 6 4 39 1) 0)
The example works in #lang datalog (which should be a subset of #lang racklog)