With the stacks counted and guarded (D-16) their size is a parameter of
the node. The host node, which runs the interpreter and the compiler
under the user's programme, gets 32 values and 32 return entries; a mesh
node keeps the F18's 10 and 9. Nothing else about the mechanism or any
word's definition changes.
- stack.h: V4_DATA_RING and V4_RET_RING are build parameters; the
Makefile sets them for the host-node tests.
- tests/test_host_quit.c no longer assumes a size: it fills the stacks to
whatever they are, and takes every exit with the return stack full.
- Measured on the host node now: 28 values on a line, 29 waiting between
lines, words 31 deep from the prompt.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Ruled 2026-10-04, revising D-2: stack overflow and underflow are errors
that are shown and return to the prompt, not silent wrap-around.
- Each stack counts what it holds. Before every opcode the executor
checks that the stacks hold what it takes and have room for what it
leaves; otherwise the opcode does nothing and the node faults, as for a
bad address, to that kind's handler. Every fault empties both stacks.
- The fault handler is now a table of five jumps: address, data overflow,
data underflow, return overflow, return underflow. The host node says
"Stack overflow", "Stack underflow", "Return stack overflow",
"Return stack underflow", then ERROR and the prompt.
- Two registers, DSTACK-DEPTH and RSTACK-DEPTH: a fetch reads the depth,
a store empties the stack. QUIT, ABORT and the error exits empty the
return stack before they call anything; ABORT empties the data stack.
- capsule/forth.v4: DEPTH, PICK and ROLL, to FORTH-79 (counting from
one). PICK and ROLL set the values above the one wanted aside in
memory, and work with the stack full.
- Division by zero now takes its operands off the stack, as v3 does.
- A colon with no room for its entry abandons the line.
- tests: every opcode at every depth of both stacks; the faults, the
registers and the three words from the prompt.
The sizes are unchanged: ten values, nine return entries.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Ruled 2026-10-04: guarded, an error shown, back to the prompt.
- capsule/forth.v4: / MOD /MOD */ */MOD M/MOD, M* and S>D join the
vocabulary. Each dividing word tests its divisor first; zero prints
v3's message ("/: Division by zero"), ends an open definition, prints
ERROR and returns to the prompt from however deep.
- SM/REM here has UM/MOD written into it and keeps its signs in memory,
and */MOD has M* written in, so that division can be used inside words
that other words call: / from four words deep, */MOD from three.
- forth.v4 now loads after quit.v4, which the guard leaves through.
- tests: v3 transcripts for each message; /MOD, /, MOD and */MOD against
C on every pair of edge values.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
The fourth layer of the compiler capsule. compile.v4: INTERPRET's
loop, STATE [ ] : ; EXIT IMMEDIATE LITERAL COMPILE [COMPILE] ' EXECUTE,
CREATE VARIABLE CONSTANT DOES>, and IF ELSE THEN BEGIN UNTIL AGAIN
WHILE REPEAT DO ?DO LOOP +LOOP on a control-flow stack in memory.
forth.v4: the first words of the vocabulary, the in-line ones.
FORTH source now goes in and running code comes out. 49 programmes
were run through the v3 binary and through this; every result agrees,
bar COMPILE, which v3 cannot run. The code laid down for each control
structure is word for word the expansion DECOMPOSITION.md gives.
A line may have six values on the stack while it is interpreted, and
words called from the interpreter may nest eight deep.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
