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rose-ash/lib/minikanren/tests/peano.sx
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mk: peano arithmetic (zeroo, pluso, minuso, *o, lteo, lto)
Classic miniKanren Peano arithmetic on (:z / (:s n)) naturals. pluso runs
relationally in all directions: 2+3=5 forward, x+2=5 → 3 backward,
enumerates the four pairs summing to 3. *o is iterated pluso. lteo/lto
via existential successor decomposition.

19 new tests, 188/188 cumulative. Phase-tagged in the plan separately
from Phase 6 CLP(FD), which will eventually replace this with native
integers + arc-consistency propagation.
2026-05-07 21:54:16 +00:00

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;; lib/minikanren/tests/peano.sx — Peano arithmetic.
;;
;; Builds Peano numbers via a host-side helper so tests stay readable.
;; (mk-nat 3) → (:s (:s (:s :z))).
(define
mk-nat
(fn (n) (if (= n 0) :z (list :s (mk-nat (- n 1))))))
;; --- zeroo ---
(mk-test
"zeroo-zero-succeeds"
(run* q (zeroo :z))
(list (make-symbol "_.0")))
(mk-test
"zeroo-non-zero-fails"
(run* q (zeroo (mk-nat 1)))
(list))
;; --- pluso forward ---
(mk-test
"pluso-forward-2-3"
(run* q (pluso (mk-nat 2) (mk-nat 3) q))
(list (mk-nat 5)))
(mk-test "pluso-forward-zero-zero" (run* q (pluso :z :z q)) (list :z))
(mk-test
"pluso-forward-zero-n"
(run* q (pluso :z (mk-nat 4) q))
(list (mk-nat 4)))
(mk-test
"pluso-forward-n-zero"
(run* q (pluso (mk-nat 4) :z q))
(list (mk-nat 4)))
;; --- pluso backward ---
(mk-test
"pluso-recover-augend"
(run* q (pluso q (mk-nat 2) (mk-nat 5)))
(list (mk-nat 3)))
(mk-test
"pluso-recover-addend"
(run* q (pluso (mk-nat 2) q (mk-nat 5)))
(list (mk-nat 3)))
(mk-test
"pluso-enumerate-pairs-summing-to-3"
(run*
q
(fresh (a b) (pluso a b (mk-nat 3)) (== q (list a b))))
(list
(list :z (mk-nat 3))
(list (mk-nat 1) (mk-nat 2))
(list (mk-nat 2) (mk-nat 1))
(list (mk-nat 3) :z)))
;; --- minuso ---
(mk-test
"minuso-5-2-3"
(run* q (minuso (mk-nat 5) (mk-nat 2) q))
(list (mk-nat 3)))
(mk-test
"minuso-n-n-zero"
(run* q (minuso (mk-nat 7) (mk-nat 7) q))
(list :z))
;; --- *o ---
(mk-test
"times-2-3"
(run* q (*o (mk-nat 2) (mk-nat 3) q))
(list (mk-nat 6)))
(mk-test
"times-zero-anything-zero"
(run* q (*o :z (mk-nat 99) q))
(list :z))
(mk-test
"times-3-4"
(run* q (*o (mk-nat 3) (mk-nat 4) q))
(list (mk-nat 12)))
;; --- lteo / lto ---
(mk-test
"lteo-success"
(run 1 q (lteo (mk-nat 2) (mk-nat 5)))
(list (make-symbol "_.0")))
(mk-test
"lteo-equal-success"
(run 1 q (lteo (mk-nat 3) (mk-nat 3)))
(list (make-symbol "_.0")))
(mk-test
"lteo-greater-fails"
(run* q (lteo (mk-nat 5) (mk-nat 2)))
(list))
(mk-test
"lto-strict-success"
(run 1 q (lto (mk-nat 2) (mk-nat 5)))
(list (make-symbol "_.0")))
(mk-test
"lto-equal-fails"
(run* q (lto (mk-nat 3) (mk-nat 3)))
(list))
(mk-tests-run!)