Every walk over a lazy seq created FRESH wrapper tables around the shared
rest-thunks (ls-rest, ls-seq/ls-count, realize-for-iteration, the printers,
reduce — each had its own make-lazy-seq loop), so independent walks re-ran
the thunks: side effects duplicated, and a doall'd seq of futures was
re-spawned serially by the deref walk. Every walker now goes through
ls-rest-cached, which memoizes the rest wrapper on its node — thunks run
exactly once, as in Clojure. Costs ~10% on walk-heavy benches (the per-node
cache get/put — Clojure's LazySeq pays the same); net still -9% vs the
pre-linear-walks baseline. Three regression rows pin once-only effects and
value stability across walks.
On top of that: pmap/pcalls/pvalues (jolt-oeu) over the real-thread futures
— spawn-all-then-deref (the once-only fix is what makes the doall actually
mean that), snapshot semantics documented, multi-coll arity via the
canonical vector-zip. System/currentTimeMillis + nanoTime land as System
statics (the realtime clock — os/time is whole seconds, which quantized
every elapsed measurement to 1000ms). Seven pmap rows incl. a generous-
margin parallelism check (4 x 200ms sleeps under 700ms after warmup).
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