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matche-pattern->expr now treats keyword patterns as literals that emit
themselves bare, rather than wrapping in (quote ...). SX keywords
self-evaluate to their string name; quoting them flips them to a
keyword type that does not unify with the bare-keyword usage at the
target site. This was visible only as a test failure on the diffo
clauses below — tightened the pattern rules.
tests/classics.sx exercises three end-to-end miniKanren programs:
- 3-friend / 3-pet permutation puzzle
- grandparent inference over a fact list (membero + fresh)
- symbolic differentiation dispatched by matche on
:x / (:+ a b) / (:* a b)
228/228 cumulative.
77 lines
2.4 KiB
Plaintext
77 lines
2.4 KiB
Plaintext
;; lib/minikanren/matche.sx — Phase 5 piece D: pattern matching over terms.
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;;
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;; (matche TARGET
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;; (PATTERN1 g1 g2 ...)
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;; (PATTERN2 g1 ...)
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;; ...)
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;;
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;; Pattern grammar:
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;; _ wildcard — fresh anonymous var
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;; x plain symbol — fresh var, bind by name
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;; ATOM literal (number, string, boolean) — must equal
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;; :keyword keyword literal — emitted bare (keywords self-evaluate
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;; to their string name in SX, so quoting them changes
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;; their type from string to keyword)
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;; () empty list — must equal
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;; (p1 p2 ... pn) list pattern — recurse on each element
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;;
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;; The macro expands to a `conde` whose clauses are
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;; `((fresh (vars-in-pat) (== target pat-expr) body...))`.
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;;
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;; Repeated symbol names within a pattern produce the same fresh var, so
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;; they unify by `==`. Fixed-length list patterns only — head/tail
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;; destructuring uses `(fresh (a d) (conso a d target) body)` directly.
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;;
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;; Note: the macro builds the expansion via `cons` / `list` rather than a
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;; quasiquote — quasiquote does not recurse into nested lambda bodies in
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;; SX, so `\`(matche-clause (quote ,target) cl)` left literal
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;; `(unquote target)` in the output.
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(define matche-symbol-var? (fn (s) (symbol? s)))
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(define
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matche-collect-vars-acc
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(fn
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(pat acc)
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(cond
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((matche-symbol-var? pat)
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(if (some (fn (s) (= s pat)) acc) acc (append acc (list pat))))
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((and (list? pat) (not (empty? pat)))
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(reduce (fn (a p) (matche-collect-vars-acc p a)) acc pat))
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(:else acc))))
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(define
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matche-collect-vars
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(fn (pat) (matche-collect-vars-acc pat (list))))
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(define
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matche-pattern->expr
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(fn
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(pat)
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(cond
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((matche-symbol-var? pat) pat)
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((and (list? pat) (empty? pat)) (list (quote list)))
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((list? pat) (cons (quote list) (map matche-pattern->expr pat)))
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((keyword? pat) pat)
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(:else (list (quote quote) pat)))))
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(define
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matche-clause
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(fn
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(target cl)
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(let
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((pat (first cl)) (body (rest cl)))
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(let
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((vars (matche-collect-vars pat)))
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(let
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((pat-expr (matche-pattern->expr pat)))
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(list
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(cons
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(quote fresh)
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(cons vars (cons (list (quote ==) target pat-expr) body)))))))))
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(defmacro
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matche
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(target &rest clauses)
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(cons (quote conde) (map (fn (cl) (matche-clause target cl)) clauses)))
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