apl: at @ replace+apply (+10 tests, 211/211)

2026-05-07 00:27:40 +00:00
parent 9eecbde61e
commit 4c71c5a75e
3 changed files with 137 additions and 2 deletions
--- a/plans/apl-on-sx.md
+++ b/plans/apl-on-sx.md
@@ -82,7 +82,7 @@ Core mapping:
 - [x] Compose `f∘g` — applies `g` first then `f`
 - [x] Power `f⍣n` — apply f n times; `f⍣≡` until fixed point
 - [x] Rank `f⍤k` — apply f at sub-rank k
- [ ] At `@` — selective replace
+- [x] At `@` — selective replace
 - [ ] 40+ tests in `lib/apl/tests/operators.sx`

 ### Phase 5 — dfns + tradfns + control flow
@@ -118,6 +118,7 @@ data; format for string templating.

 _Newest first._

+- 2026-05-07: Phase 4 step 10 — at @ (apl-at-replace + apl-at-apply); linear-index lookup, scalar-vals broadcast; 211/211 tests
 - 2026-05-07: Phase 4 step 9 — rank f⍤k (apl-rank); cell decomposition + reassembly via frame/cell shapes; 201/201 tests
 - 2026-05-06: Phase 4 step 8 — power f⍣n (apl-power) + fixed-point f⍣≡ (apl-power-fixed); 191/191 tests
 - 2026-05-06: Phase 4 step 7 — compose f∘g (apl-compose monadic f∘g x, apl-compose-dyadic dyadic f x (g y)); 182/182 tests