Brummel
e5f9828a04
Inner LetRec capturing outer LetRec's params now lifts cleanly via
the existing post-order traversal — outer's params are KnownType
in inner's outer-scope, so 16b.2's fast-path handles them. Inner
LetRec capturing outer's NAME remains rejected (closure-of-self
in body, deferred separately).
Plus hardening: lift.rs's deferred path tracks the outer LetRec
name in a parallel `enclosing_letrec_names` set so the symmetric
inner-captures-outer-name rejection fires there too — without it
a silent lift produced a runtime arity mismatch.
- examples/nested_let_rec.{ailx,ail.json}: outer counts down via
inner that captures the outer's threshold param.
- desugar.rs: clarified panic message for outer-name capture.
- lift.rs: enclosing_letrec_names tracking.
- e2e + desugar tests: 120 → 122 (+2).
End-of-16b series: feature-complete except for closure-of-self
in body and closure-with-polymorphism, both queued separately.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
54 lines
1.8 KiB
Plaintext
54 lines
1.8 KiB
Plaintext
; Iter 16b.7 — nested LetRec mutual capture (params, not name).
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;
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; `nested_sum(n)` returns the sum 1 + 2 + ... + n by combining two
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; recursive helpers. The OUTER let-rec `outer(i)` iterates i over
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; 1..=n; for each i it calls the INNER let-rec `inner(j)` to count
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; how many integers are in 1..=i (= i). The total is then
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; 1 + 2 + ... + n = n*(n+1)/2.
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;
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; The shape exercises:
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; - outer captures `n` from `nested_sum`'s fn-params (16b.2 case).
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; - inner captures `i` from outer LetRec's PARAMS (16b.7 case
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; under iter — outer LetRec's params are KnownType in body
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; scope, so the inner lift sees a resolvable capture type).
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; - inner does NOT capture outer's NAME (still rejected in 16b.7).
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;
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; Expected stdout (one per line):
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; nested_sum(1) = 1
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; nested_sum(3) = 6
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; nested_sum(5) = 15
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(module nested_let_rec
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(fn nested_sum
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(doc "Sum 1 + 2 + ... + n by nested LetRec helpers; inner captures outer's param i.")
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(type (fn-type (params (con Int)) (ret (con Int))))
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(params n)
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(body
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(let-rec outer
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(params i)
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(type (fn-type (params (con Int)) (ret (con Int))))
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(body
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(if (app > i n)
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0
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(app +
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(let-rec inner
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(params j)
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(type (fn-type (params (con Int)) (ret (con Int))))
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(body
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(if (app > j i)
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0
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(app + 1 (app inner (app + j 1)))))
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(in (app inner 1)))
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(app outer (app + i 1)))))
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(in (app outer 1)))))
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(fn main
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(doc "Drive nested_sum at 1, 3, 5. Expected (per line): 1, 6, 15.")
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(type (fn-type (params) (ret (con Unit)) (effects IO)))
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(params)
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(body
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(seq (do io/print_int (app nested_sum 1))
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(seq (do io/print_int (app nested_sum 3))
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(do io/print_int (app nested_sum 5)))))))
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