Both blockers recorded at the previous resume point turned out to be
resolvable, not permanent:
- The "cell is unbounded int" blocker for D+/D-/DNEGATE/etc. was stale --
cell was already migrated to a 64-bit word type in commit fe6e705, before
this file was first touched. The note was never re-checked against
current StarForth_Base.thy before being carried forward. Same lesson the
control_words.c vm_ip finding taught one file earlier in this sweep:
re-verify carried-forward reasoning against the current file, don't just
trust a previous session's note.
- The missing vm->ecw_nesting field for 2>R/2R>/2R@ was a real, scoped gap
-- added ecw_nesting :: nat to vm_state in StarForth_Base.thy.
Adds S>D, D+, D-, DNEGATE, DABS, a d_compare helper, DMAX, DMIN, D<, D=,
D0=, D0<, D2*, D2/, 2>R, 2R>, 2R@. D2*/D2/ use push_bit/drop_bit/bit
(established idiom from StarForth_Q48_16.thy) for the 128-bit shifts; D2/
uses sint/div (floor division) rather than cell_sdiv (C99 truncating
division) since arithmetic right shift is floor division, not truncation,
for negative operands. DNEGATE's double-negation-is-identity property is
true but left unproved (needs the same carry/borrow-across-the-pair
algebra as D+/D-, not just simp) -- a nice-to-have, not core plumbing.
All 20 registered words in double_words.c are now covered. 28 theory
files verify with zero errors.
Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
Covers the pure double-cell data-stack shuffle words from
src/word_source/double_words.c. Deliberately scoped to exclude:
- 2>R/2R>/2R@: branch on vm->ecw_nesting, a field vm_state doesn't track
at all -- needs a model extension first, not attempted here.
- S>D/D+/D-/DNEGATE/DABS/DMAX/DMIN/D</D=/D0=/D0</D2*/D2/: depend on
cell_t being a fixed-width (64-bit) wrapping integer (explicit
unsigned-long carry/borrow arithmetic, bitwise complement with
wraparound). StarForth_Base.thy's "cell = int" is unbounded, not
fixed-width, so this isn't expressible as currently modeled. Fixing it
means deciding whether cell becomes a 64-bit word type everywhere
(ripples into all 23 already-verified theories) -- a foundational
decision, flagged for later, not made as a side effect of this file.
24 theory files now verify with zero errors.
