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rose-ash/lib/datalog/tests/negation.sx
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datalog: stratified negation (Phase 7, 124/124)
New lib/datalog/strata.sx: dl-build-dep-graph (relation -> deps with
:neg flag), Floyd-Warshall reachability, SCC-via-mutual-reach for
non-stratifiability detection, iterative dl-compute-strata, and
dl-group-rules-by-stratum.

eval.sx refactor:
- dl-saturate-rules! db rules — semi-naive worker over a rule subset
- dl-saturate! db — stratified driver. Rejects non-stratifiable
  programs at saturation time, then iterates strata in order
- dl-match-negation — succeeds iff inner positive match is empty

Order-aware safety in dl-rule-check-safety (Phase 4) already
required negation vars to be bound by a prior positive literal.
Stratum dict keys are strings (SX dicts don't accept ints).

Phase 6 magic sets deferred — opt-in path, semi-naive default
suffices for current workloads.
2026-05-08 08:20:56 +00:00

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;; lib/datalog/tests/negation.sx — stratified negation tests.
(define dl-nt-pass 0)
(define dl-nt-fail 0)
(define dl-nt-failures (list))
(define
dl-nt-deep=?
(fn
(a b)
(cond
((and (list? a) (list? b))
(and (= (len a) (len b)) (dl-nt-deq-l? a b 0)))
((and (dict? a) (dict? b))
(let ((ka (keys a)) (kb (keys b)))
(and (= (len ka) (len kb)) (dl-nt-deq-d? a b ka 0))))
((and (number? a) (number? b)) (= a b))
(else (equal? a b)))))
(define
dl-nt-deq-l?
(fn
(a b i)
(cond
((>= i (len a)) true)
((not (dl-nt-deep=? (nth a i) (nth b i))) false)
(else (dl-nt-deq-l? a b (+ i 1))))))
(define
dl-nt-deq-d?
(fn
(a b ka i)
(cond
((>= i (len ka)) true)
((let ((k (nth ka i)))
(not (dl-nt-deep=? (get a k) (get b k))))
false)
(else (dl-nt-deq-d? a b ka (+ i 1))))))
(define
dl-nt-set=?
(fn
(a b)
(and
(= (len a) (len b))
(dl-nt-subset? a b)
(dl-nt-subset? b a))))
(define
dl-nt-subset?
(fn
(xs ys)
(cond
((= (len xs) 0) true)
((not (dl-nt-contains? ys (first xs))) false)
(else (dl-nt-subset? (rest xs) ys)))))
(define
dl-nt-contains?
(fn
(xs target)
(cond
((= (len xs) 0) false)
((dl-nt-deep=? (first xs) target) true)
(else (dl-nt-contains? (rest xs) target)))))
(define
dl-nt-test!
(fn
(name got expected)
(if
(dl-nt-deep=? got expected)
(set! dl-nt-pass (+ dl-nt-pass 1))
(do
(set! dl-nt-fail (+ dl-nt-fail 1))
(append!
dl-nt-failures
(str
name
"\n expected: " expected
"\n got: " got))))))
(define
dl-nt-test-set!
(fn
(name got expected)
(if
(dl-nt-set=? got expected)
(set! dl-nt-pass (+ dl-nt-pass 1))
(do
(set! dl-nt-fail (+ dl-nt-fail 1))
(append!
dl-nt-failures
(str
name
"\n expected (set): " expected
"\n got: " got))))))
(define
dl-nt-throws?
(fn
(thunk)
(let
((threw false))
(do
(guard
(e (#t (set! threw true)))
(thunk))
threw))))
(define
dl-nt-run-all!
(fn
()
(do
;; Negation against EDB-only relation.
(dl-nt-test-set! "not against EDB"
(dl-query
(dl-program
"p(1). p(2). p(3). r(2).
q(X) :- p(X), not(r(X)).")
(list (quote q) (quote X)))
(list {:X 1} {:X 3}))
;; Negation against derived relation — needs stratification.
(dl-nt-test-set! "not against derived rel"
(dl-query
(dl-program
"p(1). p(2). p(3). s(2).
r(X) :- s(X).
q(X) :- p(X), not(r(X)).")
(list (quote q) (quote X)))
(list {:X 1} {:X 3}))
;; Two-step strata: r derives via s; q derives via not r.
(dl-nt-test-set! "two-step strata"
(dl-query
(dl-program
"node(a). node(b). node(c). node(d).
edge(a, b). edge(b, c). edge(c, a).
reach(X, Y) :- edge(X, Y).
reach(X, Z) :- edge(X, Y), reach(Y, Z).
unreachable(X) :- node(X), not(reach(a, X)).")
(list (quote unreachable) (quote X)))
(list {:X (quote d)}))
;; Combine negation with arithmetic and comparison.
(dl-nt-test-set! "negation with arithmetic"
(dl-query
(dl-program
"n(1). n(2). n(3). n(4). n(5). odd(1). odd(3). odd(5).
even(X) :- n(X), not(odd(X)).")
(list (quote even) (quote X)))
(list {:X 2} {:X 4}))
;; Empty negation result.
(dl-nt-test-set! "negation always succeeds"
(dl-query
(dl-program
"p(1). p(2). q(X) :- p(X), not(r(X)).")
(list (quote q) (quote X)))
(list {:X 1} {:X 2}))
;; Negation always fails.
(dl-nt-test-set! "negation always fails"
(dl-query
(dl-program
"p(1). p(2). r(1). r(2). q(X) :- p(X), not(r(X)).")
(list (quote q) (quote X)))
(list))
;; Stratifiability checks.
(dl-nt-test! "non-stratifiable rejected"
(dl-nt-throws?
(fn ()
(let ((db (dl-make-db)))
(do
(dl-add-rule!
db
{:head (list (quote p) (quote X))
:body (list (list (quote q) (quote X))
{:neg (list (quote r) (quote X))})})
(dl-add-rule!
db
{:head (list (quote r) (quote X))
:body (list (list (quote p) (quote X)))})
(dl-add-fact! db (list (quote q) 1))
(dl-saturate! db)))))
true)
(dl-nt-test! "stratifiable accepted"
(dl-nt-throws?
(fn ()
(dl-program
"p(1). p(2). r(2).
q(X) :- p(X), not(r(X)).")))
false)
;; Multi-stratum chain.
(dl-nt-test-set! "three-level strata"
(dl-query
(dl-program
"a(1). a(2). a(3). a(4).
b(X) :- a(X), not(c(X)).
c(X) :- d(X).
d(2).
d(4).")
(list (quote b) (quote X)))
(list {:X 1} {:X 3}))
;; Safety violation: negation refers to unbound var.
(dl-nt-test! "negation safety violation"
(dl-nt-throws?
(fn ()
(dl-program
"p(1). q(X) :- p(X), not(r(Y)).")))
true))))
(define
dl-negation-tests-run!
(fn
()
(do
(set! dl-nt-pass 0)
(set! dl-nt-fail 0)
(set! dl-nt-failures (list))
(dl-nt-run-all!)
{:passed dl-nt-pass
:failed dl-nt-fail
:total (+ dl-nt-pass dl-nt-fail)
:failures dl-nt-failures})))