giles
1d7400a54a
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Solves the canonical cyclic-graph divergence problem from the deferred plan. Naive memoization (table-1/2/3 in tabling.sx) drains the body's answer stream eagerly; cyclic recursive calls with the same ground key diverge before populating the cache. table-2-slg / table-3-slg add an in-progress sentinel: before evaluating the body, mark the cache entry :in-progress. Any recursive call to the same key sees the sentinel and returns mzero (no answers yet). Outer recursion thus terminates on cycles. After the body finishes, the sentinel is replaced with the actual answer-value list. Demo: tab-patho with a 3-edge graph (a -> b, b -> a, b -> c). (run* q (tab-patho :a :c q)) -> ((:a :b :c)) ; finite (run* q (tab-patho :a :a q)) -> ((:a :b :a)) ; one cycle visit (run* q (tab-patho :a :b q)) -> ((:a :b)) ; direct edge Without SLG, all three diverge. Limitation: single-pass — answers found by cycle-dependent recursive calls are not iteratively re-discovered. Full SLG with fixed-point iteration (re-running until no new answers) is left for follow-up. 5 new tests including SLG-fib for sanity (matches naive table-2), 3 cyclic patho cases.