mk: phase 1 — unify.sx + 48 tests, kit-driven

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.

lib/minikanren/tests/unify.sx

@@ -0,0 +1,293 @@
+;; lib/minikanren/tests/unify.sx — Phase 1 tests for unify.sx.
+;;
+;; Loads into a session that already has lib/guest/match.sx and
+;; lib/minikanren/unify.sx defined. Tests are top-level forms.
+;; Call (mk-tests-run!) afterwards to get the totals.
+;;
+;; Note: SX dict equality is reference-based, so tests check the *effect*
+;; of a unification (success/failure flag, or walked bindings) rather than
+;; the raw substitution dict.
+
+(define mk-test-pass 0)
+(define mk-test-fail 0)
+(define mk-test-fails (list))
+
+(define
+  mk-test
+  (fn
+    (name actual expected)
+    (if
+      (= actual expected)
+      (set! mk-test-pass (+ mk-test-pass 1))
+      (begin
+        (set! mk-test-fail (+ mk-test-fail 1))
+        (append! mk-test-fails {:name name :expected expected :actual actual})))))
+
+(define mk-tests-run! (fn () {:total (+ mk-test-pass mk-test-fail) :passed mk-test-pass :failed mk-test-fail :fails mk-test-fails}))
+
+(define mk-unified? (fn (s) (if (= s nil) false true)))
+
+;; --- fresh variable construction ---
+
+(mk-test
+  "make-var-distinct"
+  (let ((a (make-var)) (b (make-var))) (= (var-name a) (var-name b)))
+  false)
+
+(mk-test "make-var-is-var" (mk-var? (make-var)) true)
+(mk-test "var?-num" (mk-var? 5) false)
+(mk-test "var?-list" (mk-var? (list 1 2)) false)
+(mk-test "var?-string" (mk-var? "hi") false)
+(mk-test "var?-empty" (mk-var? (list)) false)
+(mk-test "var?-bool" (mk-var? true) false)
+
+;; --- empty substitution ---
+
+(mk-test "empty-s-walk-num" (mk-walk 5 empty-s) 5)
+(mk-test "empty-s-walk-str" (mk-walk "x" empty-s) "x")
+(mk-test
+  "empty-s-walk-list"
+  (mk-walk (list 1 2) empty-s)
+  (list 1 2))
+(mk-test
+  "empty-s-walk-unbound-var"
+  (let ((x (make-var))) (= (mk-walk x empty-s) x))
+  true)
+
+;; --- walk: top-level chain resolution ---
+
+(mk-test
+  "walk-direct-binding"
+  (mk-walk (mk-var "x") (extend "x" 7 empty-s))
+  7)
+
+(mk-test
+  "walk-two-step-chain"
+  (mk-walk
+    (mk-var "x")
+    (extend "x" (mk-var "y") (extend "y" 9 empty-s)))
+  9)
+
+(mk-test
+  "walk-three-step-chain"
+  (mk-walk
+    (mk-var "a")
+    (extend
+      "a"
+      (mk-var "b")
+      (extend "b" (mk-var "c") (extend "c" 42 empty-s))))
+  42)
+
+(mk-test
+  "walk-stops-at-list"
+  (mk-walk (list 1 (mk-var "x")) (extend "x" 5 empty-s))
+  (list 1 (mk-var "x")))
+
+;; --- walk*: deep walk into lists ---
+
+(mk-test
+  "walk*-flat-list-with-vars"
+  (mk-walk*
+    (list (mk-var "x") 2 (mk-var "y"))
+    (extend "x" 1 (extend "y" 3 empty-s)))
+  (list 1 2 3))
+
+(mk-test
+  "walk*-nested-list"
+  (mk-walk*
+    (list 1 (mk-var "x") (list 2 (mk-var "y")))
+    (extend "x" 5 (extend "y" 6 empty-s)))
+  (list 1 5 (list 2 6)))
+
+(mk-test
+  "walk*-unbound-stays-var"
+  (let
+    ((x (mk-var "x")))
+    (= (mk-walk* (list 1 x) empty-s) (list 1 x)))
+  true)
+
+(mk-test "walk*-atom" (mk-walk* 5 empty-s) 5)
+
+;; --- unify atoms (success / failure semantics, not dict shape) ---
+
+(mk-test
+  "unify-num-eq-succeeds"
+  (mk-unified? (mk-unify 5 5 empty-s))
+  true)
+(mk-test "unify-num-neq-fails" (mk-unify 5 6 empty-s) nil)
+(mk-test
+  "unify-str-eq-succeeds"
+  (mk-unified? (mk-unify "a" "a" empty-s))
+  true)
+(mk-test "unify-str-neq-fails" (mk-unify "a" "b" empty-s) nil)
+(mk-test
+  "unify-bool-eq-succeeds"
+  (mk-unified? (mk-unify true true empty-s))
+  true)
+(mk-test "unify-bool-neq-fails" (mk-unify true false empty-s) nil)
+(mk-test
+  "unify-nil-eq-succeeds"
+  (mk-unified? (mk-unify nil nil empty-s))
+  true)
+(mk-test
+  "unify-empty-list-succeeds"
+  (mk-unified? (mk-unify (list) (list) empty-s))
+  true)
+
+;; --- unify var with anything (walk to verify binding) ---
+
+(mk-test
+  "unify-var-num-binds"
+  (mk-walk (mk-var "x") (mk-unify (mk-var "x") 5 empty-s))
+  5)
+
+(mk-test
+  "unify-num-var-binds"
+  (mk-walk (mk-var "x") (mk-unify 5 (mk-var "x") empty-s))
+  5)
+
+(mk-test
+  "unify-var-list-binds"
+  (mk-walk
+    (mk-var "x")
+    (mk-unify (mk-var "x") (list 1 2) empty-s))
+  (list 1 2))
+
+(mk-test
+  "unify-var-var-same-no-extend"
+  (mk-unified? (mk-unify (mk-var "x") (mk-var "x") empty-s))
+  true)
+
+(mk-test
+  "unify-var-var-different-walks-equal"
+  (let
+    ((s (mk-unify (mk-var "x") (mk-var "y") empty-s)))
+    (= (mk-walk (mk-var "x") s) (mk-walk (mk-var "y") s)))
+  true)
+
+;; --- unify lists positionally ---
+
+(mk-test
+  "unify-list-equal-succeeds"
+  (mk-unified?
+    (mk-unify
+      (list 1 2 3)
+      (list 1 2 3)
+      empty-s))
+  true)
+
+(mk-test
+  "unify-list-different-length-fails-1"
+  (mk-unify
+    (list 1 2)
+    (list 1 2 3)
+    empty-s)
+  nil)
+
+(mk-test
+  "unify-list-different-length-fails-2"
+  (mk-unify
+    (list 1 2 3)
+    (list 1 2)
+    empty-s)
+  nil)
+
+(mk-test
+  "unify-list-mismatch-fails"
+  (mk-unify
+    (list 1 2)
+    (list 1 3)
+    empty-s)
+  nil)
+
+(mk-test
+  "unify-list-vs-atom-fails"
+  (mk-unify (list 1 2) 5 empty-s)
+  nil)
+
+(mk-test
+  "unify-empty-vs-non-empty-fails"
+  (mk-unify (list) (list 1) empty-s)
+  nil)
+
+(mk-test
+  "unify-list-with-vars-walks"
+  (mk-walk*
+    (list (mk-var "x") (mk-var "y"))
+    (mk-unify
+      (list (mk-var "x") (mk-var "y"))
+      (list 1 2)
+      empty-s))
+  (list 1 2))
+
+(mk-test
+  "unify-nested-lists-with-vars-walks"
+  (mk-walk*
+    (list (mk-var "x") (list (mk-var "y") 3))
+    (mk-unify
+      (list (mk-var "x") (list (mk-var "y") 3))
+      (list 1 (list 2 3))
+      empty-s))
+  (list 1 (list 2 3)))
+
+;; --- unify chained substitutions ---
+
+(mk-test
+  "unify-chain-var-var-then-atom"
+  (let
+    ((x (mk-var "x")) (y (mk-var "y")))
+    (let
+      ((s1 (mk-unify x y empty-s)))
+      (mk-walk x (mk-unify y 7 s1))))
+  7)
+
+(mk-test
+  "unify-already-bound-consistent"
+  (let
+    ((s (extend "x" 5 empty-s)))
+    (mk-unified? (mk-unify (mk-var "x") 5 s)))
+  true)
+
+(mk-test
+  "unify-already-bound-conflict-fails"
+  (let
+    ((s (extend "x" 5 empty-s)))
+    (mk-unify (mk-var "x") 6 s))
+  nil)
+
+;; --- occurs check (opt-in) ---
+
+(mk-test
+  "unify-no-occurs-default-succeeds"
+  (let
+    ((x (mk-var "x")))
+    (mk-unified? (mk-unify x (list 1 x) empty-s)))
+  true)
+
+(mk-test
+  "unify-occurs-direct-fails"
+  (let ((x (mk-var "x"))) (mk-unify-check x (list 1 x) empty-s))
+  nil)
+
+(mk-test
+  "unify-occurs-nested-fails"
+  (let
+    ((x (mk-var "x")))
+    (mk-unify-check x (list 1 (list 2 x)) empty-s))
+  nil)
+
+(mk-test
+  "unify-occurs-non-occurring-succeeds"
+  (let
+    ((x (mk-var "x")))
+    (mk-unified? (mk-unify-check x 5 empty-s)))
+  true)
+
+(mk-test
+  "unify-occurs-via-chain-fails"
+  (let
+    ((x (mk-var "x")) (y (mk-var "y")))
+    (let ((s (extend "y" (list x) empty-s))) (mk-unify-check x y s)))
+  nil)
+
+(mk-tests-run!)

lib/minikanren/unify.sx

@@ -0,0 +1,52 @@
+;; lib/minikanren/unify.sx — Phase 1: variables + unification.
+;;
+;; miniKanren-on-SX, built on lib/guest/match.sx. The kit ships the heavy
+;; lifting (walk-with, unify-with, occurs-with, extend, empty-subst,
+;; mk-var/is-var?/var-name); this file supplies a miniKanren-shaped cfg
+;; and a thin public API.
+;;
+;; Term shape (designed for natural SX use):
+;;   logic var  : (:var NAME)              — kit's mk-var
+;;   pair       : any non-empty SX list    — head + tail unified positionally
+;;   atom       : number / string / symbol / boolean / nil / ()
+;; Substitution: SX dict mapping VAR-NAME → term. Empty = (empty-subst).
+
+(define
+  mk-list-pair?
+  (fn (t) (and (list? t) (not (empty? t)) (not (is-var? t)))))
+
+(define mk-list-pair-head (fn (t) :pair))
+(define mk-list-pair-args (fn (t) t))
+
+(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})
+
+(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})
+
+(define empty-s (empty-subst))
+
+(define mk-fresh-counter 0)
+
+(define
+  make-var
+  (fn
+    ()
+    (begin
+      (set! mk-fresh-counter (+ mk-fresh-counter 1))
+      (mk-var (str "_." mk-fresh-counter)))))
+
+(define mk-var? is-var?)
+
+(define mk-walk (fn (t s) (walk-with mk-cfg t s)))
+
+(define
+  mk-walk*
+  (fn
+    (t s)
+    (let
+      ((w (mk-walk t s)))
+      (cond
+        ((mk-list-pair? w) (map (fn (a) (mk-walk* a s)) w))
+        (:else w)))))
+
+(define mk-unify (fn (u v s) (unify-with mk-cfg u v s)))
+(define mk-unify-check (fn (u v s) (unify-with mk-cfg-occurs u v s)))

plans/minikanren-on-sx.md

@@ -50,15 +50,15 @@ Key semantic mappings:
 ## Roadmap
 
 ### Phase 1 — variables + unification
-- [ ] `make-var` → fresh logic variable (unique mutable box)
-- [ ] `var?` `v` → bool — is this a logic variable?
-- [ ] `walk` `term` `subst` → follow substitution chain to ground term or unbound var
-- [ ] `walk*` `term` `subst` → deep walk (recurse into lists/dicts)
-- [ ] `unify` `u` `v` `subst` → extended substitution or `#f` (failure)
+- [x] `make-var` → fresh logic variable (unique mutable box)
+- [x] `var?` `v` → bool — is this a logic variable?
+- [x] `walk` `term` `subst` → follow substitution chain to ground term or unbound var
+- [x] `walk*` `term` `subst` → deep walk (recurse into lists/dicts)
+- [x] `unify` `u` `v` `subst` → extended substitution or `#f` (failure)
       Handles: var/var, var/term, term/var, list unification, number/string/symbol equality.
       No occurs check by default; `unify-check` with occurs check as opt-in.
-- [ ] Empty substitution `empty-s` = `(list)` (empty assoc list)
-- [ ] Tests in `lib/minikanren/tests/unify.sx`: ground terms, vars, lists, failure, occurs
+- [x] Empty substitution `empty-s` (dict-based via kit's `empty-subst` — assoc list was a sketch; kit ships dict, kept it)
+- [x] Tests in `lib/minikanren/tests/unify.sx`: ground terms, vars, lists, failure, occurs
 
 ### Phase 2 — streams + goals
 - [ ] Stream type: `mzero` (empty stream = `nil`), `unit s` (singleton = `(list s)`),
@@ -135,4 +135,12 @@ _(none yet)_
 
 _Newest first._
 
-_(awaiting phase 1)_
+- **2026-05-07** — **Phase 1 done**: `lib/minikanren/unify.sx` (53 lines, ~22 lines of actual code) +
+  `lib/minikanren/tests/unify.sx` (48 tests, all green). Kit consumption: `walk-with`,
+  `unify-with`, `occurs-with`, `extend`, `empty-subst`, `mk-var`, `is-var?`, `var-name`
+  all supplied by `lib/guest/match.sx`. Local additions: a miniKanren-flavoured cfg
+  (treats native SX lists as cons-pairs via `:ctor-head = :pair`, occurs-check off),
+  `make-var` fresh-counter, deep `mk-walk*` (kit's `walk*` only recurses into `:ctor`
+  form, not native lists), and `mk-unify` / `mk-unify-check` thin wrappers. The kit
+  earns its keep ~3× over by line count — confirms lib-guest match kit is reusable
+  for logic-language hosts as designed.