Single-call entry: dl-eval source-string query-string parses
both, builds a db via dl-program, saturates implicitly, runs
the query (extracted from the parsed `?- ...` clause), and
returns the substitution list.
Most user-friendly path:
(dl-eval "parent(a, b). ..." "?- ancestor(a, X).")
2 new api tests cover ancestor and multi-goal usage.
dl-query now auto-dispatches on the first element's shape:
- positive literal (head is a symbol) or {:neg ...} dict → wrap
- list of literals → conjunctive query
dl-query-coerce normalizes; dl-query-user-vars collects the union
of user-named vars (deduped, '_' filtered) for projection. Old
single-literal callers unchanged.
(dl-query db '(p X)) ; single
(dl-query db '((p X) (q X))) ; conjunction
(dl-query db (list '(n X) '(> X 2))) ; with comparison
2 new api tests cover multi-goal AND and conjunction with comparison.
New lib/datalog/api.sx: dl-program-data facts rules takes SX data
lists. Rules accept either dict form or list form using <- as the
rule arrow (since SX parses :- as a keyword). dl-rule constructor
for the dict shape. dl-assert! adds a fact and re-saturates;
dl-retract! drops EDB matches, wipes all rule-headed IDB
relations, and re-saturates from scratch — simplest correct
semantics until provenance tracking arrives.
9 API tests cover ancestor closure via data, dict-rule form,
dl-rule constructor, incremental assert/retract, cyclic-graph
reach, assert into empty, fact-style rule (no arrow), dict
passthrough.
