Adds the two canonical prefix-slicing combinators to std_list.
First fns in std_list to combine `if` + Int arithmetic + recursive
ADT pattern in one body.
take : forall a. (Int, List<a>) -> List<a>
— first n elements (or all of xs if shorter than n).
drop : forall a. (Int, List<a>) -> List<a>
— list with first n elements removed (Nil if n >= length).
Both use `(if (<= n 0) ...)` as the base-case guard since
literal sub-patterns inside Ctor patterns aren't yet supported
(queued as 16c — would let take/drop collapse the if into the
match).
examples/std_list_more_demo: builds [1, 2, 3, 4, 5] once and
exercises take/drop at n=0, n=mid, n=overflow on each. Expected
output 0, 3, 5, 5, 3, 0 (one per line).
Tests: 95/95 (e2e went from 35 to 36). std_list grew from 10 to
12 combinators; total stdlib 5 modules / 29 combinators. No new
compiler bug surfaced.
Pre-existing std_list defs are byte-identical (verified via diff
on .ailx and round-trip on .ail.json), so the five downstream
importers (std_list_demo, std_list_stress, std_either_list,
std_either_list_demo, list_map_poly) need no regeneration.
Brummel
ee5807d73c