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core: Phase 5 Option A — lazy interleave/reductions/tree-seq via letfn

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These three were the last eager transformers, blocked by jolt-r81: a self-
recursive lazy-seq in the overlay leaks its macro expansion under :compile? when
recursion goes through a top-level name or (fn name …) self-name. Rewriting the
recursion as letfn-bound (the form partition-by/mapcat/dedupe already use, which
compiles cleanly) sidesteps the bug. All three are now lazy in interpret,
compile, and self-host — completing Option A for every transformer.

interleave: canonical lazy cons-recursion (2-arity) + map/concat (n-arity).
reductions: letfn step accumulator. tree-seq: letfn walk + lazy mapcat.

Gate: conformance 246x3, lazy-infinite 40/40 (+interleave/reductions/tree-seq
infinite cases), fixpoint, self-host, specs+unit green.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
This commit is contained in:
Yogthos 2026-06-08 17:28:55 -04:00
parent 3a42438b68
commit c7e162add4
2 changed files with 49 additions and 40 deletions
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5
test/integration/lazy-infinite-test.janet
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@ -47,8 +47,9 @@
["first filter even? drop range" "4" "(first (filter even? (drop 3 (range))))"]
["take 3 remove odd? range" "(quote (0 2 4))" "(take 3 (remove odd? (range)))"]
["take 3 drop-while <5 range" "(quote (5 6 7))" "(take 3 (drop-while (fn [x] (< x 5)) (range)))"]
# interleave stays eager in overlay (lazy-seq macro breaks compile mode).
# ["take 4 interleave range iterate" "(quote (0 10 1 11))" "(take 4 (interleave (range) (iterate inc 10)))"]
["take 4 interleave range iterate" "(quote (0 10 1 11))" "(take 4 (interleave (range) (iterate inc 10)))"]
["take 4 reductions + range" "(quote (0 1 3 6))" "(take 4 (reductions + (range)))"]
["take 3 tree-seq infinite" "(quote (0 0 0))" "(take 3 (tree-seq (fn [_] true) (fn [n] [n]) 0))"]
["take 3 partition 2 range" "(quote ((0 1) (2 3) (4 5)))" "(take 3 (partition 2 (range)))"]
["take 3 partition-all 2 range" "(quote ((0 1) (2 3) (4 5)))" "(take 3 (partition-all 2 (range)))"]
["take 3 map-indexed vector range" "(quote ([0 0] [1 1] [2 2]))" "(take 3 (map-indexed vector (range)))"]