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Demonstrates the naive-patho behaviour on a 2-cycle (a <-> b, plus b -> c). Without Phase-7 tabling, the search produces ever-longer paths: (a b), (a b a b), (a b a b a b), ... `run 5` truncates to a finite prefix; `run*` diverges. Documenting this as a regression-style test gives Phase 7 a concrete starting point. 3 new tests, 331/331 cumulative.
49 lines
1.2 KiB
Plaintext
49 lines
1.2 KiB
Plaintext
;; lib/minikanren/tests/cyclic-graph.sx — demonstrates the naive-patho
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;; behaviour on a cyclic graph. Without Phase-7 tabling/SLG, the search
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;; produces ever-longer paths revisiting the cycle. `run n` truncates;
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;; `run*` would diverge.
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(define cyclic-edges (list (list :a :b) (list :b :a) (list :b :c)))
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(define cyclic-edgeo (fn (x y) (membero (list x y) cyclic-edges)))
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(define
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cyclic-patho
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(fn
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(x y path)
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(conde
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((cyclic-edgeo x y) (== path (list x y)))
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((fresh (z mid) (cyclic-edgeo x z) (cyclic-patho z y mid) (conso x mid path))))))
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;; --- direct edge ---
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(mk-test
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"cyclic-direct"
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(run 1 q (cyclic-patho :a :b q))
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(list (list :a :b)))
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;; --- runs first 5 paths from a to b: bare edge, then increasing
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;; numbers of cycle traversals (a->b->a->b, etc.) ---
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(mk-test
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"cyclic-enumerates-prefix-via-run-n"
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(let
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((paths (run 5 q (cyclic-patho :a :b q))))
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(and
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(= (len paths) 5)
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(and
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(every? (fn (p) (= (first p) :a)) paths)
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(every? (fn (p) (= (last p) :b)) paths))))
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true)
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(mk-test
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"cyclic-finds-c-via-cycle-or-direct"
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(let
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((paths (run 3 q (cyclic-patho :a :c q))))
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(and
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(>= (len paths) 1)
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(some (fn (p) (= p (list :a :b :c))) paths)))
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true)
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(mk-tests-run!)
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