-- Bio-shaped window walk — exercises the eager `window n xs` path on a
-- `chars`-derived list (Text typed, heap-string elements). PR-2 reshapes
-- the dispatcher to emit `L (ListView)` aliasing the source: each stride
-- is O(1) instead of O(n) clone_rcs. Microbenches that previously took
-- 4-6 seconds finish in 0.2s on the same machine.
--
-- The shape mirrors the bioinformatics `has-tm` predicate that surfaced
-- the original perf cliff:
-- `cs = chars s; ws = window 15 cs; flt all-h ws`
-- This file walks a smaller variant so it can run in CI alongside every
-- engine (tree-walker, VM dispatcher, Cranelift JIT). All three must
-- agree: the producer reshape is VM-side, the AOT helper still emits real
-- Lists, and Cranelift bails the OP_WINDOW arm to the VM dispatcher.
-- A 15-element predicate over a small char run. The window consumer is a
-- closure that reads via `len`, indices, and `flt`+`is-hydro` — all read
-- paths that PR-1 migrated to handle ListView.
is-hydro c:t>b;has "AILMFWVYC" c
all-h xs:L t>b;n=len (flt is-hydro xs);=n 15
count-hydro-windows s:t>n
cs=chars s
ws=window 15 cs
ms=flt all-h ws
len ms
main>n
-- 30 chars, all hydrophobic in `AILMFWVYC`. The 15-wide window hits the
-- all-hydrophobic predicate at every stride (30 - 15 + 1 = 16 of them).
-- 25 hydrophobic chars then a non-hydrophobic K. Each 15-wide window
-- that excludes K (positions 0..10 inclusive) matches; the rest fail.
count-hydro-windows "AAAAAAAAAAAAAAAILMFWVYCAK"
-- run: main
-- out: 10