Brummel
a4be1e58a3
Iteration-discipline milestone, 2 of 3. Strictly additive (nothing tail-related removed; that is it.3). New whole-body pass verify_structural_recursion sibling of verify_tail_positions (DD-1): smaller-set algorithm with implicit candidate inference + unconstrained accumulators (DD-2, foldl=structural), self/mutual via inline ADT-family union-find (DD-3), it.2-only tail==false grandfather. CheckError::NonStructuralRecursion. term_contains_loop (stops at Term::Lam, DD-4) injects Diverge so existing UndeclaredEffect enforces it, no new variant; lam-arrow + LetRec sub-effect sites wired. DESIGN.md Decision 3 synced. Four it.1 loop fixtures gained !Diverge. Two spec-premise boundary defects surfaced + resolved within the additive invariant (corpus clean, check not weakened), recorded as corrected it.3 corpus-migration scope: (1) the "21 tail-app fixtures" grandfather premise under-counts the corpus — no-ADT-candidate counter recursions have no structural position to verify, deferred to it.3; (2) two RC-regression fixtures joined the spec's transitional tail-app grandfather as the other 20 do (RC==GC guards verified still green). cargo test --workspace 622/0; 9 acceptance pins non-vacuous. Specfda9b78, planbc9f512.
25 lines
757 B
Plaintext
25 lines
757 B
Plaintext
; Iter it.2 positive: structural list length. `len` recurses on the
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; Cons-tail `t` (a constructor sub-component of `xs`) via a plain,
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; non-tail `(app len t)`. Structurally guarded at position 0, pure,
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; total, Diverge-free. No `tail-app` marker — this is the structural
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; recursion form the it.2 guardedness check must accept on its own.
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(module struct_rec_list_len
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(data IntList
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(ctor INil)
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(ctor ICons (con Int) (con IntList)))
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(fn len
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(doc "Length of an IntList via structural recursion on the tail.")
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(type
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(fn-type
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(params (con IntList))
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(ret (con Int))))
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(params xs)
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(body
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(match xs
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(case (pat-ctor INil) 0)
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(case (pat-ctor ICons h t)
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(app + 1 (app len t)))))))
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