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rose-ash/lib/minikanren/relations.sx
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mk: partitiono — split list by predicate
(partitiono pred l yes no) — yes is the elements of l where pred
succeeds; no is the rest. Conde dispatches on each element via the
predicate goal vs nafc-of-the-predicate, threading the head through
the matching output list.

Composes with intarith / membero / etc. for any predicate-shaped goal:
  (partitiono (fn (x) (lto-i x 5)) (list 1 7 2 8 3) yes no)
    yes -> (1 2 3); no -> (7 8)

5 new tests, 496/496 cumulative.
2026-05-08 12:18:25 +00:00

306 lines
6.9 KiB
Plaintext

;; lib/minikanren/relations.sx — Phase 4 standard relations.
;;
;; Programs use native SX lists as data. Relations decompose lists via the
;; tagged cons-cell shape `(:cons h t)` because SX has no improper pairs;
;; the unifier treats `(:cons h t)` and the native list `(h . t)` as
;; equivalent, and `mk-walk*` flattens cons cells back to flat lists for
;; reification.
;; --- pair / list shape relations ---
(define nullo (fn (l) (== l (list))))
(define pairo (fn (p) (fresh (a d) (== p (mk-cons a d)))))
(define caro (fn (p a) (fresh (d) (== p (mk-cons a d)))))
(define cdro (fn (p d) (fresh (a) (== p (mk-cons a d)))))
(define conso (fn (a d p) (== p (mk-cons a d))))
(define firsto caro)
(define resto cdro)
(define
listo
(fn (l) (conde ((nullo l)) ((fresh (a d) (conso a d l) (listo d))))))
;; --- appendo: the canary ---
;;
;; (appendo l s ls) — `ls` is the concatenation of `l` and `s`.
;; Runs forwards (l, s known → ls), backwards (ls known → all (l, s) pairs),
;; and bidirectionally (mix of bound + unbound).
(define
appendo
(fn
(l s ls)
(conde
((nullo l) (== s ls))
((fresh (a d res) (conso a d l) (conso a res ls) (appendo d s res))))))
;; --- membero ---
;; (membero x l) — x appears (at least once) in l.
(define
appendo3
(fn
(l1 l2 l3 result)
(fresh (l12) (appendo l1 l2 l12) (appendo l12 l3 result))))
(define
partitiono
(fn
(pred l yes no)
(conde
((nullo l) (nullo yes) (nullo no))
((fresh (a d y-rest n-rest) (conso a d l) (conde ((pred a) (conso a y-rest yes) (== no n-rest) (partitiono pred d y-rest n-rest)) ((nafc (pred a)) (== yes y-rest) (conso a n-rest no) (partitiono pred d y-rest n-rest))))))))
(define
membero
(fn
(x l)
(conde
((fresh (d) (conso x d l)))
((fresh (a d) (conso a d l) (membero x d))))))
(define
not-membero
(fn
(x l)
(conde
((nullo l))
((fresh (a d) (conso a d l) (nafc (== a x)) (not-membero x d))))))
(define
subseto
(fn
(l1 l2)
(conde
((nullo l1))
((fresh (a d) (conso a d l1) (membero a l2) (subseto d l2))))))
(define
reverseo
(fn
(l r)
(conde
((nullo l) (nullo r))
((fresh (a d res-rev) (conso a d l) (reverseo d res-rev) (appendo res-rev (list a) r))))))
(define
rev-acco
(fn
(l acc result)
(conde
((nullo l) (== result acc))
((fresh (a d acc-prime) (conso a d l) (conso a acc acc-prime) (rev-acco d acc-prime result))))))
(define rev-2o (fn (l result) (rev-acco l (list) result)))
(define palindromeo (fn (l) (fresh (rev) (reverseo l rev) (== l rev))))
(define prefixo (fn (p l) (fresh (rest) (appendo p rest l))))
(define suffixo (fn (s l) (fresh (front) (appendo front s l))))
(define
subo
(fn
(s l)
(fresh
(front-and-s back front)
(appendo front-and-s back l)
(appendo front s front-and-s))))
(define
selecto
(fn
(x rest l)
(conde
((conso x rest l))
((fresh (a d r) (conso a d l) (conso a r rest) (selecto x r d))))))
(define
lengtho
(fn
(l n)
(conde
((nullo l) (== n :z))
((fresh (a d n-1) (conso a d l) (== n (list :s n-1)) (lengtho d n-1))))))
(define
inserto
(fn
(a l p)
(conde
((conso a l p))
((fresh (h t pt) (conso h t l) (conso h pt p) (inserto a t pt))))))
(define
permuteo
(fn
(l p)
(conde
((nullo l) (nullo p))
((fresh (a d perm-d) (conso a d l) (permuteo d perm-d) (inserto a perm-d p))))))
(define
flatteno
(fn
(tree flat)
(conde
((nullo tree) (nullo flat))
((pairo tree)
(fresh
(h t hf tf)
(conso h t tree)
(flatteno h hf)
(flatteno t tf)
(appendo hf tf flat)))
((nafc (nullo tree)) (nafc (pairo tree)) (== flat (list tree))))))
(define
rembero
(fn
(x l out)
(conde
((nullo l) (nullo out))
((fresh (a d) (conso a d l) (== a x) (== out d)))
((fresh (a d res) (conso a d l) (nafc (== a x)) (conso a res out) (rembero x d res))))))
(define
removeo-allo
(fn
(x l result)
(conde
((nullo l) (nullo result))
((fresh (a d) (conso a d l) (== a x) (removeo-allo x d result)))
((fresh (a d r-rest) (conso a d l) (nafc (== a x)) (conso a r-rest result) (removeo-allo x d r-rest))))))
(define
assoco
(fn
(key pairs val)
(fresh
(rest)
(conde
((conso (list key val) rest pairs))
((fresh (other) (conso other rest pairs) (assoco key rest val)))))))
(define
nth-o
(fn
(n l elem)
(conde
((== n :z) (fresh (d) (conso elem d l)))
((fresh (n-1 a d) (== n (list :s n-1)) (conso a d l) (nth-o n-1 d elem))))))
(define
samelengtho
(fn
(l1 l2)
(conde
((nullo l1) (nullo l2))
((fresh (a d a-prime d-prime) (conso a d l1) (conso a-prime d-prime l2) (samelengtho d d-prime))))))
(define
mapo
(fn
(rel l1 l2)
(conde
((nullo l1) (nullo l2))
((fresh (a d a-prime d-prime) (conso a d l1) (conso a-prime d-prime l2) (rel a a-prime) (mapo rel d d-prime))))))
(define
iterate-no
(fn
(rel n x result)
(conde
((== n :z) (== result x))
((fresh (n-1 mid) (== n (list :s n-1)) (rel x mid) (iterate-no rel n-1 mid result))))))
(define
pairlisto
(fn
(l1 l2 pairs)
(conde
((nullo l1) (nullo l2) (nullo pairs))
((fresh (a1 d1 a2 d2 d-pairs) (conso a1 d1 l1) (conso a2 d2 l2) (conso (list a1 a2) d-pairs pairs) (pairlisto d1 d2 d-pairs))))))
(define
swap-firsto
(fn
(l result)
(fresh
(a b rest mid-l mid-r)
(conso a mid-l l)
(conso b rest mid-l)
(conso b mid-r result)
(conso a rest mid-r))))
(define
everyo
(fn
(rel l)
(conde
((nullo l))
((fresh (a d) (conso a d l) (rel a) (everyo rel d))))))
(define
someo
(fn
(rel l)
(conde
((fresh (a d) (conso a d l) (rel a)))
((fresh (a d) (conso a d l) (someo rel d))))))
(define
lasto
(fn
(l x)
(conde
((conso x (list) l))
((fresh (a d) (conso a d l) (lasto d x))))))
(define
init-o
(fn
(l init)
(conde
((fresh (x) (conso x (list) l) (== init (list))))
((fresh (a d d-init) (conso a d l) (conso a d-init init) (init-o d d-init))))))
(define
tako
(fn
(n l prefix)
(conde
((== n :z) (== prefix (list)))
((fresh (n-1 a d p-rest) (== n (list :s n-1)) (conso a d l) (conso a p-rest prefix) (tako n-1 d p-rest))))))
(define
dropo
(fn
(n l suffix)
(conde
((== n :z) (== suffix l))
((fresh (n-1 a d) (== n (list :s n-1)) (conso a d l) (dropo n-1 d suffix))))))
(define
repeato
(fn
(x n result)
(conde
((== n :z) (== result (list)))
((fresh (n-1 r-rest) (== n (list :s n-1)) (conso x r-rest result) (repeato x n-1 r-rest))))))
(define
concato
(fn
(lists result)
(conde
((nullo lists) (nullo result))
((fresh (h t r-rest) (conso h t lists) (appendo h r-rest result) (concato t r-rest))))))