3 Parenthetical Datalog Module Language

 #lang datalog/sexp

The semantics of this language is the same as the normal Datalog language, except it uses the parenthetical syntax described in Racket Interoperability.

All identifiers in racket/base are available for use as predicate symbols or constant values. Top-level identifiers and datums are not otherwise allowed in the program. The program may contain require expressions.

The following is a program:
#lang datalog/sexp
(! (edge a b))
(! (edge b c))
(! (edge c d))
(! (edge d a))
(! (:- (path X Y)
       (edge X Y)))
(! (:- (path X Y)
       (edge X Z)
       (path Z Y)))
(? (path X Y))

This is also a program:
#lang datalog/sexp
(require racket/math)
(? (sqr 4 :- X))

The Parenthetical Datalog REPL accepts new statements that are executed as if they were in the original program text, except require is not allowed.