feat(v4.0.0): vocabularies, to FORTH-79

- VOCABULARY DEFINITIONS CONTEXT CURRENT FORTH, and v3's ORDER.  A name is
  looked up in the CONTEXT vocabulary and then in FORTH; a new entry goes
  into the CURRENT vocabulary; : makes the CURRENT vocabulary CONTEXT;
  FORTH is immediate.
- WORDS lists the CONTEXT vocabulary.  FORGET takes what was defined later
  out of every vocabulary, and a vocabulary that goes gives way to FORTH.
- v3's vocabularies separate nothing: a word defined in one is found from
  every other, and one redefined in a vocabulary replaces FORTH's for good.
- tests/test_host_quit.c: isolation, chaining to FORTH, two vocabularies
  with the same names, FORGET across them; and DUMP is now checked to put
  BASE back.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

v4/capsule/system.v4

@@ -6,16 +6,57 @@
 \ Constants the loader supplies:
 \   FENCE   word address of the variable: FORGET will not remove an entry
 \           that starts below the address it holds
+\   VOC-LINK   word address of the variable: the newest vocabulary, or 0
 
 header FENCE inline     : FENCE'  FENCE ;
 
-\ ( -- )   the names in the dictionary, the newest first, a blank after
+\ ---- vocabularies (FORTH-79) ----------------------------------------------------
+\ A vocabulary is two cells: its head -- the xt of its newest entry, or 0 --
+\ and the address of the vocabulary defined before it, or 0.  VOC-LINK holds
+\ the newest one's address.  FORTH's head is (LATEST) and it is in no chain.
+header CONTEXT inline   : CONTEXT'  CONTEXT ;
+header CURRENT inline   : CURRENT'  CURRENT ;
+
+\ FORTH-79: the primary vocabulary; it becomes the CONTEXT vocabulary.
+header FORTH immediate
+: FORTH         (LATEST) CONTEXT a! ! ;
+\ FORTH-79: new definitions go into the CONTEXT vocabulary from now on.
+header DEFINITIONS
+: DEFINITIONS   CONTEXT a! @ CURRENT a! ! ;
+
+\ VOCABULARY xxx   FORTH-79: xxx is a new, empty list of words; executing
+\ xxx makes it the CONTEXT vocabulary.  When a search of it finds nothing,
+\ FORTH is searched.
+: (DOVOC)   pop CONTEXT a! ! ;
+header VOCABULARY
+: VOCABULARY
+  &(DOVOC) (C)+3 a! !  (DATA)  (C)+8 a! @ if NONE  drop
+  0 ,  VOC-LINK a! @ ,  HERE -2 + VOC-LINK a! ! ;
+  NONE: drop ;
+
+\ ( cell -- )   print the name of the vocabulary whose head cell this is
+: (.VOC)
+  dup (LATEST) xor if F  drop  -1 + -2 + a! @ 4*  COUNT 31 and  jump TYPE
+  F: drop drop  $54524F46 (EMIT4) $48 (EMIT4) ;
+
+\ ( -- )   as v3's, but true: where names are looked for, and where new ones go
+header ORDER
+: ORDER
+  $72616553 (EMIT4) $6F206863 (EMIT4) $72656472 (EMIT4) $203A (EMIT4)
+  CONTEXT a! @  dup (.VOC) SPACE
+  (LATEST) xor if ONLY  drop  (LATEST) (.VOC)  jump TWO
+  ONLY: drop
+  TWO: CR
+  $72727543 (EMIT4) $3A746E65 (EMIT4) $20 (EMIT4)
+  CURRENT a! @ (.VOC)  jump CR
+
+\ ( -- )   the names in the CONTEXT vocabulary, the newest first, a blank after
 \ each, a new line whenever one has passed column 64.  Hidden entries -- a
 \ definition under way -- are not shown.  (Q)+0 is the column.
 header WORDS
 : WORDS
   0 (Q) a! !
-  LATEST
+  CONTEXT a! @ a! @
   L: if DONE
      dup -3 + a! @ 2 and if SHOW  drop jump NXT
      SHOW: drop
@@ -29,17 +70,37 @@ header WORDS
 header VLIST
 : VLIST   jump WORDS
 
-\ FORGET xxx   FORTH-79: remove xxx and every word defined after it.  The
-\ space they took is free again.  A word that is not there is an error, and
-\ so is one below FENCE, which is where the capsule's own words are (code
-\ 10, "Protected word").
+\ ( cell -- )   take off a vocabulary's list every entry at or above the
+\ address in (Q)+0.  The newest are first, so it stops at the first one below.
+: (PRUNE)
+  (Q)+1 a! !
+  L: (Q)+1 a! @ a! @  if DONE
+     dup (Q) a! @ inv + 1 + -if CUT  drop drop ;
+     CUT: drop  -1 + a! @  (Q)+1 a! @ a! !  jump L
+  DONE: drop ;
+
+\ FORGET xxx   FORTH-79: remove xxx and every word defined after it, in
+\ whatever vocabulary; the space they took is free again.  A vocabulary that
+\ goes is no longer CONTEXT or CURRENT: FORTH is.  A word that is not there
+\ is an error, and so is one below FENCE, which is where the capsule's own
+\ words are (code 10, "Protected word").
 header FORGET
 : FORGET
   32 WORD (LOOKUP) if MISSING
-  dup -2 + a! @                              \ xt name
+  -2 + a! @                                  \ where its name starts
   dup FENCE a! @ inv + 1 + -if OK            \ name - fence
-    drop drop drop  NODE-ERROR b! 10 !b ;
+    drop drop  NODE-ERROR b! 10 !b ;
   OK: drop
-  4* DP a! !                                 \ the space from its name on
-  -1 + a! @ (LATEST) a! ! ;                  \ and the entry before it is the newest
+  dup (Q) a! !  4* DP a! !                   \ the space from its name on
+  (LATEST) (PRUNE)
+  V: VOC-LINK a! @ if PRUNED                 \ vocabularies that go
+     dup (Q) a! @ inv + 1 + -if GONE  drop jump KEPT
+     GONE: drop  1 + a! @  VOC-LINK a! !  jump V
+  KEPT: P: if PRUNED                         \ the lists of those that stay
+     dup (PRUNE)  1 + a! @  jump P
+  PRUNED: drop
+  CONTEXT a! @ (Q) a! @ inv + 1 + -if C1  drop jump C2
+  C1: drop  (LATEST) CONTEXT a! !
+  C2: CURRENT a! @ (Q) a! @ inv + 1 + -if C3  drop ;
+  C3: drop  (LATEST) CURRENT a! ! ;
   MISSING: drop  (UNKNOWN) drop ;