forth: Phase 4 strings — S"/C"/."/TYPE/COUNT/CMOVE/FILL/BLANK (+16; Hayes 168/590)

plans/forth-on-sx.md

@@ -78,7 +78,7 @@ Representation:
 - [x] Baseline: probably 30-50% Core passing after phase 3
 
 ### Phase 4 — strings + more Core
-- [ ] `S"`, `C"`, `."`, `TYPE`, `COUNT`, `CMOVE`, `FILL`, `BLANK`
+- [x] `S"`, `C"`, `."`, `TYPE`, `COUNT`, `CMOVE`, `FILL`, `BLANK`
 - [ ] `CHAR`, `[CHAR]`, `KEY`, `ACCEPT`
 - [ ] `BASE` manipulation: `DECIMAL`, `HEX`
 - [ ] `DEPTH`, `SP@`, `SP!`
@@ -99,6 +99,20 @@ Representation:
 
 _Newest first._
 
+- **Phase 4 — strings: `S"`/`C"`/`."`/`TYPE`/`COUNT`/`CMOVE`/`CMOVE>`/`MOVE`/`FILL`/`BLANK`/`C@`/`C!`/`CHAR+`/`CHARS` (+16 / Hayes 165→168).**
+  Added a byte-addressable memory model to state: `mem` (dict keyed by
+  stringified address → integer byte) and `here` (next-free integer
+  addr). Helpers `forth-alloc-bytes!` / `forth-mem-write-string!` /
+  `forth-mem-read-string`. `S"`/`C"`/`."` are IMMEDIATE parsing words
+  that consume tokens until one ends with `"`, then either copy content
+  into memory at compile time (and emit a push of `addr`/`addr len` for
+  the colon-def body) or do it inline in interpret mode. `TYPE` emits
+  `u` bytes from `addr` via `char-from-code`. `COUNT` reads the length
+  byte at a counted-string address and pushes (`addr+1`, `u`). `FILL`,
+  `BLANK` (FILL with space), `CMOVE` (forward), `CMOVE>` (backward),
+  and `MOVE` (auto-directional) mutate the byte dict. 193/193 internal
+  tests, Hayes 168/590 (+3).
+
 - **Phase 3 — Hayes conformance runner + baseline scoreboard (165/590, 28%).**
   `lib/forth/conformance.sh` preprocesses `ans-tests/core.fr` (strips `\`
   and `( ... )` comments + `TESTING` lines), splits the source on every