Robert Allan James
cb4326c712
Adds LINE (Bresenham in raster space, endpoints projected once each -- valid because the cavalier projection is linear), CIRCLE/ELLIPSE (36-segment polygon approximation), and ARC (18 segments over a caller radian range) to capsules/fabric.4th (blocks 4903-4912). TO-RASTER factored out of CART-PLOT (same behavior) so LINE can reuse the projection+flip for both endpoints. Found mid-implementation: colon definitions cannot span block boundaries in this capsule loader -- verified with a throwaway test capsule, the continuation lands in a [CAPSULE][DEFER] path that never resolves. LINE's body is split across LINE-SETUP/LINE-DONE?/LINE-STUCK?/LINE-STEP, each self-contained within its block, rather than one long definition. A fourth real bug, serious this time: CIRCLE's first live test rendered only one quadrant, then hung the VM for several minutes on a follow-up call. Root cause: q48_to_u64() (include/q48_16.h and include/starkernel/q48_16.h, backing Q.TO-INT) did an unsigned logical shift, corrupting any negative Q48.16 value into a huge garbage integer instead of sign-extending -- inevitable once Q.SIN/Q.COS leave the first quadrant. That garbage became a bogus LINE target with no bound on LINE-STEP's Bresenham loop. Fixed q48_to_u64 to shift through a signed int64_t intermediate (bit-identical for the non-negative case). Also added LINE-STUCK? (LSTEPS vs FB-WIDTH+FB-HEIGHT, the true worst case for an on-screen line) as a defense-in-depth cap against any future bad target. Verified live on amd64 after both fixes: -65536 Q.TO-INT . now prints -1; LINE/CIRCLE/ARC/ELLIPSE all complete without hanging or erroring, and a combined screendump shows all four rendering correctly and distinctly. All three architectures boot clean to ok> with the DoE completing; dict_hash identical across all three and unchanged from 4.3.3a (expected -- fabric.4th isn't loaded at boot, and the Q.TO-INT fix doesn't change dictionary structure). FABRIC.md item 4.3.3b marked done with full acceptance evidence.
capsules/
FORTH personality files loaded by the VM at boot. A capsule is an immutable, content-addressed payload; its XXHash64 hash is its identity. Any mutation changes the hash and the birth protocol rejects the image.
Key files
| File | Type | Purpose |
|---|---|---|
init.4th |
(m) MAMA_INIT |
Default Mama VM personality — loaded at LBN 2048 |
ACL.4th |
user | Word-level ACL system; self-activating at boot |
zuse.4th |
user | Bootstrap superuser; loaded by ACL.4th |
doe.4th |
user | DoE workload words (EXEC-DOE) — opt-in |
init-0.4th … init-9.4th |
(p) |
Numbered personality variants |
init-l8-*.4th |
(p) |
L8 Jacquard mode variants (stable/volatile/diverse/temporal/transition/omni) |
hermes/init.4th |
(p) |
Hermes baby VM personality |
artemis/init.4th |
(p) |
Artemis baby VM personality |
Block namespace
Block ranges are shared across all loaded capsules — collisions cause silent word-definition overwrites.
| Range | Owner |
|---|---|
| 2048–2099 | init.4th |
| 2100–2199 | doe.4th |
| 3000–3999 | workload capsules |
| 4000+ | user-defined (ACL.4th, zuse.4th, …) |
Each block is limited to 1024 bytes. Verify with wc -c before committing.
See also
experiments/bare_metal/README.md— DoE protocols and block namespace rulesdocs/03-architecture/word-acl/DESIGN.md— ACL system designtools/mkcapsule.c— assembles capsules intocapsule_generated.c- Project root