-- window n xs:L a > L (L a) — sliding windows of size n.
-- Each element is a consecutive n-sized sub-list of xs.
-- n > len xs returns []. n must be a positive integer.
-- Basic 3-wide window over 5 elements
basic>L (L n);window 3 [1, 2, 3, 4, 5]
-- 2-wide pairs (moving pair)
pairs>L (L n);window 2 [10, 20, 30]
-- Single-element windows
singles>L (L n);window 1 [1, 2, 3]
-- n larger than list → empty list
toobig>L (L n);window 5 [1, 2, 3]
-- 3-element moving sum: window then map sum.
-- Cross-engine: map with a builtin HOF callback now works on every engine
-- (FnRef NaN-tagging + native `map` lift; see #274 and the PR 2 follow-up).
sums>L n;map sum (window 3 [1, 2, 3, 4, 5])
-- run: basic
-- out: [[1, 2, 3], [2, 3, 4], [3, 4, 5]]
-- run: pairs
-- out: [[10, 20], [20, 30]]
-- run: singles
-- out: [[1], [2], [3]]
-- run: toobig
-- out: []
-- run: sums
-- out: [6, 9, 12]