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lib/minikanren/unify.sx wraps lib/guest/match.sx with a miniKanren-flavoured cfg: native SX lists as cons-pairs, occurs-check off by default. ~22 lines of local logic over kit's walk-with / unify-with / extend / occurs-with. 48 tests in lib/minikanren/tests/unify.sx exercise: var fresh-distinct, walk chains, walk* deep into nested lists, atom/var/list unification with positional matching, failure modes, opt-in occurs check.
53 lines
1.7 KiB
Plaintext
53 lines
1.7 KiB
Plaintext
;; lib/minikanren/unify.sx — Phase 1: variables + unification.
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;;
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;; miniKanren-on-SX, built on lib/guest/match.sx. The kit ships the heavy
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;; lifting (walk-with, unify-with, occurs-with, extend, empty-subst,
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;; mk-var/is-var?/var-name); this file supplies a miniKanren-shaped cfg
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;; and a thin public API.
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;;
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;; Term shape (designed for natural SX use):
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;; logic var : (:var NAME) — kit's mk-var
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;; pair : any non-empty SX list — head + tail unified positionally
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;; atom : number / string / symbol / boolean / nil / ()
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;; Substitution: SX dict mapping VAR-NAME → term. Empty = (empty-subst).
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(define
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mk-list-pair?
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(fn (t) (and (list? t) (not (empty? t)) (not (is-var? t)))))
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(define mk-list-pair-head (fn (t) :pair))
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(define mk-list-pair-args (fn (t) t))
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(define mk-cfg {:ctor-head mk-list-pair-head :var? is-var? :ctor? mk-list-pair? :occurs-check? false :var-name var-name :ctor-args mk-list-pair-args})
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(define mk-cfg-occurs {:ctor-head mk-list-pair-head :var? is-var? :ctor? mk-list-pair? :occurs-check? true :var-name var-name :ctor-args mk-list-pair-args})
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(define empty-s (empty-subst))
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(define mk-fresh-counter 0)
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(define
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make-var
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(fn
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()
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(begin
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(set! mk-fresh-counter (+ mk-fresh-counter 1))
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(mk-var (str "_." mk-fresh-counter)))))
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(define mk-var? is-var?)
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(define mk-walk (fn (t s) (walk-with mk-cfg t s)))
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(define
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mk-walk*
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(fn
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(t s)
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(let
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((w (mk-walk t s)))
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(cond
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((mk-list-pair? w) (map (fn (a) (mk-walk* a s)) w))
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(:else w)))))
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(define mk-unify (fn (u v s) (unify-with mk-cfg u v s)))
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(define mk-unify-check (fn (u v s) (unify-with mk-cfg-occurs u v s)))
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