Hare's delete also takes a slicing place (harec check.c:1981-2027
EXPR_SLICE; Hare spells it delete(xs[i..j])): remove [lo, hi) — shift
[hi..len) down count = hi-lo strides, len -= count, cap unchanged; lo
defaults 0, hi defaults len, so delete(xs[:]) clears the slice with
storage retained. Checker accepts N_SLICE next to N_INDEX (object must
chase to a slice, harec :2024); the old range-unimplemented reject and
its #35 cite drop.
Lowering (both stages, converged byte-identical by construction) is the
single-element arm's same-slice whole-stride word-copy loop with a
DYNAMIC src offset (count*esz via a src register) instead of the
constant one-stride. Base shapes: local slice ident, deref-of-local,
plus NEW indexed local-slice base xs[g][lo:hi] — the fold-5a consumer
shape (regex.ha:333 delete(jump_idxs[group_level][..]); outer stride
off the type table). Bounds stay implicit, inheriting the documented
single-element posture (no index checks anywhere in cgen). Operands
evaluate left-to-right, exactly once, before the shift (harec order);
only the header ADDRESS is taken before operand eval, so a bound
expression's writes through the slice land before the copy.
test/809: 64 fixtures — full/explicit/re-clear/head/mid/tail/empty
a:a/end-boundary len:len/explicit 0:0 on a never-appended (nil-ptr)
slice, single-vs-range equivalence, cap preservation, esz 1/2/4/8/16/24
copy tails against the dynamic src, operand order-of-eval (lo/hi CALLs
fire once each, in order) + aliasing-visibility pins, the EXACT
[][]size regex consumer shape, deref base, 2 reject rows w/ diagnostic
text; every accept row cs==ww asm byte-id. test/804: reject_range row
retired (form now accepted), reject_nonindex text follows the widened
message.
A BUILD_FAIL row now asserts the expected stderr substring on both
stages (the #35 cite on the range form included) — without it a row
passes vacuously on any unrelated build failure. The new
delete_in_loop row drains [1,2,3,4] to empty via repeated
delete(xs[0]) with base-4 positional accumulation, pinning the len
bookkeeping under iteration. 38 -> 41 fixtures.
Hare's delete(xs[i]) (ref/harec/src/check.c:1981-2027): checker accepts
an N_INDEX over a slice-typed base, stamps void; loud-rejects the range
form delete(xs[i..j]) (stays filed on #35 — regex fold-2b's consumers
are all single-element), non-index operands, array bases, wrong arity.
Lowering (both stages, converged byte-identical by construction):
ascending word-copy loop shifts [i+1..len) down one esz stride, then
hdr.len -= 1; cap unchanged. The move is a same-type whole-stride byte
copy — src and dst are elements of the SAME slice, so no boxing exists
for any element kind; one loop serves scalar/narrow/str/struct/tagged.
esz off the STAMPED base type (#34/#48 discipline). Base shapes: local
slice ident (LEAQ) and deref-of-local ptr-to-slice (MOVQ — the fold-2b
delete_thread shape); others rule-7 loud-stop.
test/804: 38 fixtures — first/middle/last/to-empty, esz 1/4/8/24/56
(MOVB/MOVL tails + 7-qword tagged), cap-unchanged, (*threads)[i], 4
checker reject rows; every accept row cs==ww asm byte-id.
