Measured, compiling a DO loop left one return entry spare under
INTERPRET and a defining word called from inside another word
overflowed the nine-entry return stack (D-2); the prompt loop will take
one more.
C@ and C! shift without a loop. The code generator shifts each opcode
into the word being built, so nothing is placed by a counted shift, and
the address masks come from a table. The dictionary search, the
in-liner, the end of a loop and the making of a data word are each one
word reached by a jump.
Every kind of line now leaves at least three return entries spare while
it compiles; a word run from the interpreter has six; and CREATE ...
DOES> works from the prompt, from a word, and from a word that calls
that.
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>
