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(fresh (x y z) g1 g2 ...) expands to a let that calls (make-var) for each named var, then mk-conjs the goals. call-fresh is the function-shaped alternative for programmatic goal building. 9 new tests: empty-vars, single var, multi-var multi-goal, fresh under disj, nested fresh, call-fresh equivalents. 91/91 cumulative.
24 lines
841 B
Plaintext
24 lines
841 B
Plaintext
;; lib/minikanren/fresh.sx — Phase 2 piece B: `fresh` for introducing
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;; logic variables inside a goal body.
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;;
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;; (fresh (x y z) goal1 goal2 ...)
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;; ≡ (let ((x (make-var)) (y (make-var)) (z (make-var)))
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;; (mk-conj goal1 goal2 ...))
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;;
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;; A macro rather than a function so user-named vars are real lexical
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;; bindings — which is also what miniKanren convention expects.
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;; The empty-vars form (fresh () goal ...) is just a goal grouping.
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(defmacro
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fresh
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(vars &rest goals)
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(quasiquote
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(let
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(unquote (map (fn (v) (list v (list (quote make-var)))) vars))
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(mk-conj (splice-unquote goals)))))
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;; call-fresh — functional alternative for code that builds goals
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;; programmatically:
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;; ((call-fresh (fn (x) (== x 7))) empty-s) → ({:_.N 7})
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(define call-fresh (fn (f) (fn (s) ((f (make-var)) s))))
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