forth: setup SYSVNXT in Forth code

Not needed anymore. CONSTANT does the trick.

emul/forth/stage.c

@@ -29,7 +29,7 @@ trouble of compiling defs to binary.
 
 //#define DEBUG
 // in sync with glue.asm
-#define RAMSTART 0x890
+#define RAMSTART 0x840
 #define STDIO_PORT 0x00
 // To know which part of RAM to dump, we listen to port 2, which at the end of
 // its compilation process, spits its HERE addr to port 2 (MSB first)

forth/core.fs

@@ -2,7 +2,7 @@
 : -^ SWAP - ;
 : [ INTERPRET 1 FLAGS ! ; IMMEDIATE
 : ] R> DROP ;
-: LIT JTBL 26 + , ;
+: LIT 34 , ;
 : LITS LIT SCPY ;
 : LIT< WORD LITS ; IMMEDIATE
 : _err LIT< word-not-found (print) ABORT ;
@@ -22,6 +22,7 @@
   "_": words starting with "_" are meant to be "private",
   that is, only used by their immediate surrondings.
 
+  LIT: 34 == LIT
   COMPILE: Tough one. Get addr of caller word (example above
   (br)) and then call LITN on it. )
 
@@ -49,11 +50,33 @@
 
 : CREATE
     (entry)            ( empty header with name )
-    [ JTBL 3 + LITN ]  ( push cellWord addr )
+    11                 ( 11 == cellWord )
     ,                  ( write it )
 ;
+
+( We run this when we're in an entry creation context. Many
+  things we need to do.
+  1. Change the code link to doesWord
+  2. Leave 2 bytes for regular cell variable.
+  3. Write down RS' RTOS to entry.
+  4. exit parent definition
+)
+: DOES>
+    ( Overwrite cellWord in CURRENT )
+    ( 63 == doesWord )
+    63 CURRENT @ !
+    ( When we have a DOES>, we forcefully place HERE to 4
+      bytes after CURRENT. This allows a DOES word to use ","
+      and "C," without messing everything up. )
+    CURRENT @ 4 + HERE !
+    ( HERE points to where we should write R> )
+    R> ,
+    ( We're done. Because we've popped RS, we'll exit parent
+      definition )
+;
+
 : VARIABLE CREATE 2 ALLOT ;
-: CONSTANT CREATE H@ ! DOES> @ ;
+: CONSTANT CREATE , DOES> @ ;
 : = CMP NOT ;
 : < CMP 0 1 - = ;
 : > CMP 1 = ;
@@ -85,17 +108,18 @@
   in dictionary.txt )
 
 : (sysv)
-    (entry)
-    ( JTBL+0 == sysvarWord )
-    [ JTBL LITN ] ,
-    ( JTBL+42 == SYSVNXT )
-    [ JTBL 42 + @ LITN ] DUP    ( a a )
     ( Get new sysv addr )
-    @ ,                         ( a )
+    ( 50 == SYSVNXT )
+    50 @ @
+    CONSTANT
     ( increase current sysv counter )
-    2 SWAP +!
+    2 50 @ +!
 ;
 
+( Set up initial SYSVNXT value, which is 2 bytes after its
+  own address )
+50 @ DUP 2 + SWAP !
+
 : ."
     LIT
     BEGIN

forth/forth.asm

@@ -1,34 +1,5 @@
-; Collapse OS' Forth
-;
-; Unlike other assembler parts of Collapse OS, this unit is one huge file.
-;
-; I do this because as Forth takes a bigger place, assembler is bound to take
-; less and less place. I am thus consolidating that assembler code in one
-; place so that I have a better visibility of what to minimize.
-;
-; I also want to reduce the featureset of the assembler so that Collapse OS
-; self-hosts in a more compact manner. File include is a big part of the
-; complexity in zasm. If we can get rid of it, we'll be more compact.
+; Collapse OS Forth's boot binary
 
-; *** ABI STABILITY ***
-;
-; This unit needs to have some of its entry points stay at a stable offset.
-; These have a comment over them indicating the expected offset. These should
-; not move until the Grand Bootstrapping operation has been completed.
-;
-; When you see random ".fill" here and there, it's to ensure that stability.
-
-; *** Defines ***
-; GETC: address of a GetC routine
-; PUTC: address of a PutC routine
-;
-; Those GetC/PutC routines are hooked through defines and have this API:
-;
-; GetC: Blocks until a character is read from the device and return that
-;       character in A.
-;
-; PutC: Write character specified in A onto the device.
-;
 ; *** Const ***
 ; Base of the Return Stack
 .equ	RS_ADDR		0xf000
@@ -65,49 +36,25 @@
 ; that we can't compile a regular variable in it. SYSVNXT points to the next
 ; free space in SYSVBUF. Then, at the word level, it's a regular sysvarWord.
 .equ	SYSVNXT		@+WORD_BUFSIZE
-.equ	SYSVBUF		@+2
-.equ	RAMEND		@+SYSV_BUFSIZE
+.equ	RAMEND		@+SYSV_BUFSIZE+2
 
 ; (HERE) usually starts at RAMEND, but in certain situations, such as in stage0,
 ; (HERE) will begin at a strategic place.
 .equ	HERE_INITIAL	RAMEND
 
-; EXECUTION MODEL
-; After having read a line through readline, we want to interpret it. As
-; a general rule, we go like this:
-;
-; 1. read single word from line
-; 2. Can we find the word in dict?
-; 3. If yes, execute that word, goto 1
-; 4. Is it a number?
-; 5. If yes, push that number to PS, goto 1
-; 6. Error: undefined word.
-;
-; EXECUTING A WORD
-;
-; At it's core, executing a word is having the wordref in IY and call
-; EXECUTE. Then, we let the word do its things. Some words are special,
-; but most of them are of the compiledWord type, and that's their execution that
-; we describe here.
-;
-; First of all, at all time during execution, the Interpreter Pointer (IP)
-; points to the wordref we're executing next.
-;
-; When we execute a compiledWord, the first thing we do is push IP to the Return
-; Stack (RS). Therefore, RS' top of stack will contain a wordref to execute
-; next, after we EXIT.
-;
-; At the end of every compiledWord is an EXIT. This pops RS, sets IP to it, and
-; continues.
-
 ; *** Stable ABI ***
 ; Those jumps below are supposed to stay at these offsets, always. If they
 ; change bootstrap binaries have to be adjusted because they rely on them.
+; Those entries are referenced directly by their offset in Forth code with a
+; comment indicating what that number refers to.
+;
 ; We're at 0 here
 	jp	forthMain
-.fill 0x08-$
-JUMPTBL:
-	jp	sysvarWord
+; 3
+	jp	find
+	nop \ nop	; unused
+	nop \ nop \ nop	; unused
+; 11
 	jp	cellWord
 	jp	compiledWord
 	jp	pushRS
@@ -115,26 +62,105 @@ JUMPTBL:
 	jp	nativeWord
 	jp	next
 	jp	chkPS
-; 24
-NUMBER:
+; 32
 	.dw	numberWord
-LIT:
 	.dw	litWord
 	.dw	INITIAL_SP
 	.dw	WORDBUF
 	jp	flagsToBC
-; 35
+; 43
 	jp	strcmp
 	.dw	RS_ADDR
 	.dw	CINPTR
 	.dw	SYSVNXT
 	.dw	FLAGS
-; 46
+; 54
 	.dw	PARSEPTR
 	.dw	HERE
 	.dw	CURRENT
+	jp	parseDecimal
+	jp	doesWord
+
+; *** Boot dict ***
+; There are only 5 words in the boot dict, but these words' offset need to be
+; stable, so they're part of the "stable ABI"
+
+; Pop previous IP from Return stack and execute it.
+; ( R:I -- )
+	.db	"EXIT"
+	.dw	0
+	.db	4
+EXIT:
+	.dw nativeWord
+	call	popRSIP
+	jp	next
+
+	.db	"(br)"
+	.dw	$-EXIT
+	.db	4
+BR:
+	.dw	nativeWord
+	ld	hl, (IP)
+	ld	e, (hl)
+	inc	hl
+	ld	d, (hl)
+	dec	hl
+	add	hl, de
+	ld	(IP), hl
+	jp	next
+
+	.db	"(?br)"
+	.dw	$-BR
+	.db	5
+CBR:
+	.dw	nativeWord
+	pop	hl
+	call	chkPS
+	ld	a, h
+	or	l
+	jr	z, BR+2		; False, branch
+	; True, skip next 2 bytes and don't branch
+	ld	hl, (IP)
+	inc	hl
+	inc	hl
+	ld	(IP), hl
+	jp	next
+
+	.db	","
+	.dw	$-CBR
+	.db	1
+WR:
+	.dw	nativeWord
+	pop	de
+	call	chkPS
+	ld	hl, (HERE)
+	ld	(hl), e
+	inc	hl
+	ld	(hl), d
+	inc	hl
+	ld	(HERE), hl
+	jp	next
+
+; ( addr -- )
+	.db "EXECUTE"
+	.dw $-WR
+	.db 7
+EXECUTE:
+	.dw nativeWord
+	pop	iy	; is a wordref
+	call	chkPS
+	ld	l, (iy)
+	ld	h, (iy+1)
+	; HL points to code pointer
+	inc	iy
+	inc	iy
+	; IY points to PFA
+	jp	(hl)	; go!
+
+; Offset: 00b8
+.out $
+; *** End of stable ABI ***
 
-; *** Code ***
 forthMain:
 	; STACK OVERFLOW PROTECTION:
 	; To avoid having to check for stack underflow after each pop operation
@@ -152,9 +178,6 @@ forthMain:
 	ld	(CURRENT), hl
 	ld	hl, HERE_INITIAL
 	ld	(HERE), hl
-	; Set up SYSVNXT
-	ld	hl, SYSVBUF
-	ld	(SYSVNXT), hl
 	ld	hl, .bootName
 	call	find
 	push	de
@@ -163,48 +186,6 @@ forthMain:
 .bootName:
 	.db	"BOOT", 0
 
-.fill 101
-
-; STABLE ABI
-; Offset: 00cd
-.out $
-; copy (HL) into DE, then exchange the two, utilising the optimised HL instructions.
-; ld must be done little endian, so least significant byte first.
-intoHL:
-	push 	de
-	ld 	e, (hl)
-	inc 	hl
-	ld 	d, (hl)
-	ex 	de, hl
-	pop 	de
-	ret
-
-; add the value of A into HL
-; affects carry flag according to the 16-bit addition, Z, S and P untouched.
-addHL:
-	push	de
-	ld 	d, 0
-	ld	e, a
-	add	hl, de
-	pop	de
-	ret
-
-; Copy string from (HL) in (DE), that is, copy bytes until a null char is
-; encountered. The null char is also copied.
-; HL and DE point to the char right after the null char.
-; B indicates the length of the copied string, including null-termination.
-strcpy:
-	ld	b, 0
-.loop:
-	ld	a, (hl)
-	ld	(de), a
-	inc	hl
-	inc	de
-	inc	b
-	or	a
-	jr	nz, .loop
-	ret
-
 ; Compares strings pointed to by HL and DE until one of them hits its null char.
 ; If equal, Z is set. If not equal, Z is reset. C is set if HL > DE
 strcmp:
@@ -229,19 +210,6 @@ strcmp:
 	; early, set otherwise)
 	ret
 
-; Given a string at (HL), move HL until it points to the end of that string.
-strskip:
-	push	bc
-	ex	af, af'
-	xor	a	; look for null char
-	ld	b, a
-	ld	c, a
-	cpir	; advances HL regardless of comparison, so goes one too far
-	dec	hl
-	ex	af, af'
-	pop	bc
-	ret
-
 ; Parse string at (HL) as a decimal value and return value in DE.
 ; Reads as many digits as it can and stop when:
 ; 1 - A non-digit character is read
@@ -323,7 +291,6 @@ parseDecimal:
 	xor	a	; set Z
 	ret
 
-; *** Support routines ***
 ; Find the entry corresponding to word where (HL) points to and sets DE to
 ; point to that entry.
 ; Z if found, NZ if not.
@@ -381,8 +348,10 @@ find:
 	dec	de \ dec de \ dec de	; prev field
 	push	de			; --> lvl 2
 	ex 	de, hl
-	call 	intoHL
-	ex 	de, hl			; DE contains prev offset
+	ld 	e, (hl)
+	inc 	hl
+	ld 	d, (hl)
+	; DE contains prev offset
 	pop	hl			; <-- lvl 2
 	; HL is prev field's addr
 	; Is offset zero?
@@ -416,26 +385,6 @@ flagsToBC:
 	dec	bc
 	ret
 
-; Write DE in (HL), advancing HL by 2.
-DEinHL:
-	ld	(hl), e
-	inc	hl
-	ld	(hl), d
-	inc	hl
-	ret
-
-; *** Stack management ***
-; The Parameter stack (PS) is maintained by SP and the Return stack (RS) is
-; maintained by IX. This allows us to generally use push and pop freely because
-; PS is the most frequently used. However, this causes a problem with routine
-; calls: because in Forth, the stack isn't balanced within each call, our return
-; offset, when placed by a CALL, messes everything up. This is one of the
-; reasons why we need stack management routines below. IX always points to RS'
-; Top Of Stack (TOS)
-;
-; This return stack contain "Interpreter pointers", that is a pointer to the
-; address of a word, as seen in a compiled list of words.
-
 ; Push value HL to RS
 pushRS:
 	inc	ix
@@ -481,30 +430,13 @@ chkPS:
 	ret	nc		; (INITIAL_SP) >= SP? good
 	jp	abortUnderflow
 
-; *** Dictionary ***
-; It's important that this part is at the end of the resulting binary.
-; A dictionary entry has this structure:
-; - Xb name. Arbitrary long number of character (but can't be bigger than
-;   input buffer, of course). not null-terminated
-; - 2b prev offset
-; - 1b size + IMMEDIATE flag
-; - 2b code pointer
-; - Parameter field (PF)
-;
-; The prev offset is the number of bytes between the prev field and the
-; previous word's code pointer.
-;
-; The size + flag indicate the size of the name field, with the 7th bit
-; being the IMMEDIATE flag.
-;
-; The code pointer point to "word routines". These routines expect to be called
-; with IY pointing to the PF. They themselves are expected to end by jumping
-; to the address at (IP). They will usually do so with "jp next".
-;
-; That's for "regular" words (words that are part of the dict chain). There are
-; also "special words", for example NUMBER, LIT, FBR, that have a slightly
-; different structure. They're also a pointer to an executable, but as for the
-; other fields, the only one they have is the "flags" field.
+abortUnderflow:
+	ld	hl, .name
+	call	find
+	push	de
+	jp	EXECUTE+2
+.name:
+	.db "(uflw)", 0
 
 ; This routine is jumped to at the end of every word. In it, we jump to current
 ; IP, but we also take care of increasing it my 2 before jumping
@@ -525,6 +457,8 @@ next:
 	jp	EXECUTE+2
 
 
+; *** Word routines ***
+
 ; Execute a word containing native code at its PF address (PFA)
 nativeWord:
 	jp	(iy)
@@ -552,13 +486,6 @@ cellWord:
 	push	iy
 	jp	next
 
-; Pushes the address in the first word of the PF
-sysvarWord:
-	ld	l, (iy)
-	ld	h, (iy+1)
-	push	hl
-	jp	next
-
 ; The word was spawned from a definition word that has a DOES>. PFA+2 (right
 ; after the actual cell) is a link to the slot right after that DOES>.
 ; Therefore, what we need to do push the cell addr like a regular cell, then
@@ -590,206 +517,26 @@ numberWord:
 litWord:
 	ld	hl, (IP)
 	push	hl
-	call	strskip
-	inc	hl		; after null termination
+	; Skip to null char
+	xor	a	; look for null char
+	ld	b, a
+	ld	c, a
+	cpir
+	; CPIR advances HL regardless of comparison, so goes one char after
+	; NULL. This is good, because that's what we want...
 	ld	(IP), hl
 	jp	next
 
-; Pop previous IP from Return stack and execute it.
-; ( R:I -- )
-	.db	"EXIT"
-	.dw	0
-	.db	4
-EXIT:
-	.dw nativeWord
-	call	popRSIP
-	jp	next
-
-.fill 30
-
-abortUnderflow:
-	ld	hl, .name
-	call	find
-	push	de
-	jp	EXECUTE+2
-.name:
-	.db "(uflw)", 0
-
-	.db	"(br)"
-	.dw	$-EXIT
-	.db	4
-BR:
-	.dw	nativeWord
-	ld	hl, (IP)
-	ld	e, (hl)
-	inc	hl
-	ld	d, (hl)
-	dec	hl
-	add	hl, de
-	ld	(IP), hl
-	jp	next
-
-.fill 72
-
-	.db	"(?br)"
-	.dw	$-BR
-	.db	5
-CBR:
-	.dw	nativeWord
-	pop	hl
-	call	chkPS
-	ld	a, h
-	or	l
-	jp	z, BR+2		; False, branch
-	; True, skip next 2 bytes and don't branch
-	ld	hl, (IP)
-	inc	hl
-	inc	hl
-	ld	(IP), hl
-	jp	next
-
-.fill 15
-
-	.db	","
-	.dw	$-CBR
-	.db	1
-WR:
-	.dw	nativeWord
-	pop	de
-	call	chkPS
-	ld	hl, (HERE)
-	call	DEinHL
-	ld	(HERE), hl
-	jp	next
-
-.fill 100
-
-; ( addr -- )
-	.db "EXECUTE"
-	.dw $-WR
-	.db 7
-; STABLE ABI
-; Offset: 0388
-.out $
-EXECUTE:
-	.dw nativeWord
-	pop	iy	; is a wordref
-	call	chkPS
-	ld	l, (iy)
-	ld	h, (iy+1)
-	; HL points to code pointer
-	inc	iy
-	inc	iy
-	; IY points to PFA
-	jp	(hl)	; go!
-
-
-.fill 77
-
-	.db "DOES>"
+.fill 6
+; *** Dict hook ***
+; This dummy dictionary entry serves two purposes:
+; 1. Allow binary grafting. Because each binary dict always end with a dummy
+;    entry, we always have a predictable prev offset for the grafter's first
+;    entry.
+; 2. Tell icore's "_c" routine where the boot binary ends. See comment there.
+	.db	"_bend"
 	.dw	$-EXECUTE
 	.db	5
-DOES:
-	.dw nativeWord
-	; We run this when we're in an entry creation context. Many things we
-	; need to do.
-	; 1. Change the code link to doesWord
-	; 2. Leave 2 bytes for regular cell variable.
-	; 3. Write down IP+2 to entry.
-	; 3. exit. we're done here.
-	ld	hl, (CURRENT)
-	ld	de, doesWord
-	call	DEinHL
-	inc	hl \ inc hl		; cell variable space
-	ld	de, (IP)
-	call	DEinHL
-	ld	(HERE), hl
-	jp	EXIT+2
 
-
-.fill 82
-
-	.db	"SCPY"
-	.dw	$-DOES
-	.db	4
-SCPY:
-	.dw	nativeWord
-	pop	hl
-	ld	de, (HERE)
-	call	strcpy
-	ld	(HERE), de
-	jp	next
-
-
-	.db	"(find)"
-	.dw	$-SCPY
-	.db	6
-; STABLE ABI
-; Offset: 047c
-.out $
-FIND_:
-	.dw	nativeWord
-	pop	hl
-	call	find
-	jr	z, .found
-	; not found
-	push	hl
-	ld	de, 0
-	push	de
-	jp	next
-.found:
-	push	de
-	ld	de, 1
-	push	de
-	jp	next
-
-.fill 41
-
-	.db	"NOT"
-	.dw	$-FIND_
-	.db	3
-NOT:
-	.dw	nativeWord
-	pop	hl
-	call	chkPS
-	ld	a, l
-	or	h
-	ld	hl, 0
-	jr	nz, .skip	; true, keep at 0
-	; false, make 1
-	inc	hl
-.skip:
-	push	hl
-	jp	next
-
-
-.fill 100
-
-	.db	"(parsed)"
-	.dw	$-NOT
-	.db	8
-PARSED:
-	.dw	nativeWord
-	pop	hl
-	call	chkPS
-	call	parseDecimal
-	jr	z, .success
-	; error
-	ld	de, 0
-	push	de	; dummy
-	push	de	; flag
-	jp	next
-.success:
-	push	de
-	ld	de, 1		; flag
-	push	de
-	jp	next
-
-
-.fill 224
-
-	.db	"_bend"
-	.dw	$-PARSED
-	.db	5
-; Offset: 0647
+; Offset: 0237
 .out $

forth/icore.fs

@@ -55,31 +55,29 @@
     ,           ( write! )
 ; IMMEDIATE
 
-: JTBL 0x08 ;
-
 : FLAGS
-    ( JTBL+44 == FLAGS )
-    [ JTBL 44 + @ LITN ]
+    ( 52 == FLAGS )
+    [ 52 @ LITN ]
 ;
 
 : (parse*)
-    ( JTBL+46 == PARSEPTR )
-    [ JTBL 46 + @ LITN ]
+    ( 54 == PARSEPTR )
+    [ 54 @ LITN ]
 ;
 
 : HERE
-    ( JTBL+48 == HERE )
-    [ JTBL 48 + @ LITN ]
+    ( 56 == HERE )
+    [ 56 @ LITN ]
 ;
 
 : CURRENT
-    ( JTBL+50 == CURRENT )
-    [ JTBL 50 + @ LITN ]
+    ( 58 == CURRENT )
+    [ 58 @ LITN ]
 ;
 
 : QUIT
     0 _c FLAGS _c ! _c (resRS)
-    LIT< INTERPRET (find) _c DROP EXECUTE
+    LIT< INTERPRET _c (find) _c DROP EXECUTE
 ;
 
 : ABORT _c (resSP) _c QUIT ;
@@ -87,7 +85,7 @@
 ( This is only the "early parser" in earlier stages. No need
   for an abort message )
 : (parse)
-    (parsed) NOT IF _c ABORT THEN
+    _c (parsed) _c NOT IF _c ABORT THEN
 ;
 
 ( a -- )
@@ -96,7 +94,7 @@
     _c DUP      ( a a )
     _c C@       ( a c )
     ( exit if null )
-    _c DUP NOT IF _c 2DROP EXIT THEN
+    _c DUP _c NOT IF _c 2DROP EXIT THEN
     _c EMIT     ( a )
     1 _c +         ( a+1 )
     AGAIN
@@ -107,8 +105,8 @@
 ;
 
 : C<
-    ( JTBL+40 == CINPTR )
-    [ JTBL 40 + @ LITN ] _c @ EXECUTE
+    ( 48 == CINPTR )
+    [ 48 @ LITN ] _c @ EXECUTE
 ;
 
 : C,
@@ -119,19 +117,19 @@
 ( The NOT is to normalize the negative/positive numbers to 1
   or 0. Hadn't we wanted to normalize, we'd have written:
   32 CMP 1 - )
-: WS? 33 _c CMP 1 _c + NOT ;
+: WS? 33 _c CMP 1 _c + _c NOT ;
 
 : TOWORD
     BEGIN
-    _c C< _c DUP _c WS? NOT IF EXIT THEN _c DROP
+    _c C< _c DUP _c WS? _c NOT IF EXIT THEN _c DROP
     AGAIN
 ;
 
 ( Read word from C<, copy to WORDBUF, null-terminate, and
   return, make HL point to WORDBUF. )
 : WORD
-    ( JTBL+30 == WORDBUF )
-    [ JTBL 30 + @ LITN ]        ( a )
+    ( 38 == WORDBUF )
+    [ 38 @ LITN ]        ( a )
     _c TOWORD                   ( a c )
     BEGIN
         ( We take advantage of the fact that char MSB is
@@ -144,13 +142,13 @@
     ( a this point, PS is: a WS )
     ( null-termination is already written )
     _c 2DROP
-    [ JTBL 30 + @ LITN ]
+    [ 38 @ LITN ]
 ;
 
 : (entry)
     _c HERE _c @    ( h )
     _c WORD         ( h s )
-    SCPY            ( h )
+    _c SCPY         ( h )
     ( Adjust HERE -1 because SCPY copies the null )
     _c HERE _c @ 1 _c - ( h h' )
     _c DUP _c HERE _c ! ( h h' )
@@ -165,7 +163,7 @@
 : INTERPRET
     BEGIN
     _c WORD
-    (find)
+    _c (find)
     IF
         1 _c FLAGS _c !
         EXECUTE
@@ -177,20 +175,20 @@
 ;
 
 : BOOT
-    LIT< (parse) (find) _c DROP _c (parse*) _c !
-    LIT< (c<) (find) NOT IF LIT< KEY (find) _c DROP THEN
-    ( JTBL+40 == CINPTR )
-    [ JTBL 40 + @ LITN ] _c !
-    LIT< (c<$) (find) IF EXECUTE ELSE _c DROP THEN
+    LIT< (parse) _c (find) _c DROP _c (parse*) _c !
+    LIT< (c<) _c (find) _c
+    NOT IF LIT< KEY _c (find) _c DROP THEN
+    ( 48 == CINPTR )
+    [ 48 @ LITN ] _c !
+    LIT< (c<$) _c (find) IF EXECUTE ELSE _c DROP THEN
     _c INTERPRET
 ;
 
 ( LITN has to be defined after the last immediate usage of
   it to avoid bootstrapping issues )
 : LITN
-    ( JTBL+24 == NUMBER )
-    _c JTBL 24 _c + ,
-    ,
+    ( 32 == NUMBER )
+    32 , ,
 ;
 
 ( : and ; have to be defined last because it can't be
@@ -200,11 +198,11 @@
 : X
     _c (entry)
     ( We cannot use LITN as IMMEDIATE because of bootstrapping
-      issues. JTBL+24 == NUMBER JTBL+6 == compiledWord )
-    [ JTBL 24 + , JTBL 6 + , ] ,
+      issues. 32 == NUMBER 14 == compiledWord )
+    [ 32 , 14 , ] ,
     BEGIN
     _c WORD
-    (find)
+    _c (find)
     ( is word )
     IF _c DUP _c IMMED? IF EXECUTE ELSE , THEN
     ( maybe number )

forth/notes.txt

@@ -0,0 +1,68 @@
+Collapse OS' Forth implementation notes
+
+*** EXECUTION MODEL
+
+After having read a line through readln, we want to interpret it. As a general
+rule, we go like this:
+
+1. read single word from line
+2. Can we find the word in dict?
+3. If yes, execute that word, goto 1
+4. Is it a number?
+5. If yes, push that number to PS, goto 1
+6. Error: undefined word.
+
+*** EXECUTING A WORD
+
+At it's core, executing a word is pushing the wordref on PS and calling EXECUTE.
+Then, we let the word do its things. Some words are special, but most of them
+are of the compiledWord type, and that's their execution that we describe here.
+
+First of all, at all time during execution, the Interpreter Pointer (IP) points
+to the wordref we're executing next.
+
+When we execute a compiledWord, the first thing we do is push IP to the Return
+Stack (RS). Therefore, RS' top of stack will contain a wordref to execute next,
+after we EXIT.
+
+At the end of every compiledWord is an EXIT. This pops RS, sets IP to it, and
+continues.
+
+*** Stack management
+
+The Parameter stack (PS) is maintained by SP and the Return stack (RS) is
+maintained by IX. This allows us to generally use push and pop freely because PS
+is the most frequently used. However, this causes a problem with routine calls:
+because in Forth, the stack isn't balanced within each call, our return offset,
+when placed by a CALL, messes everything up. This is one of the reasons why we
+need stack management routines below. IX always points to RS' Top Of Stack (TOS)
+
+This return stack contain "Interpreter pointers", that is a pointer to the
+address of a word, as seen in a compiled list of words.
+
+*** Dictionary
+
+A dictionary entry has this structure:
+
+- Xb name. Arbitrary long number of character (but can't be bigger than
+  input buffer, of course). not null-terminated
+- 2b prev offset
+- 1b size + IMMEDIATE flag
+- 2b code pointer
+- Parameter field (PF)
+
+The prev offset is the number of bytes between the prev field and the previous
+word's code pointer.
+
+The size + flag indicate the size of the name field, with the 7th bit being the
+IMMEDIATE flag.
+
+The code pointer point to "word routines". These routines expect to be called
+with IY pointing to the PF. They themselves are expected to end by jumping to
+the address at (IP). They will usually do so with "jp next".
+
+That's for "regular" words (words that are part of the dict chain). There are
+also "special words", for example NUMBER, LIT, FBR, that have a slightly
+different structure. They're also a pointer to an executable, but as for the
+other fields, the only one they have is the "flags" field.
+

forth/z80a.fs

@@ -39,6 +39,9 @@
 : OP1 CREATE C, DOES> C@ A, ;
 0xeb OP1 EXDEHL,
 0x76 OP1 HALT,
+0xe9 OP1 JP(HL),
+0x12 OP1 LD(DE)A,
+0x1a OP1 LDA(DE),
 0xc9 OP1 RET,
 0x17 OP1 RLA,
 0x07 OP1 RLCA,
@@ -241,19 +244,19 @@
     SPLITB A, A,
 ;
 
-( JTBL+18 == next )
-: JPNEXT, [ JTBL 18 + LITN ] JPnn, ;
+( 26 == next )
+: JPNEXT, 26 JPnn, ;
 
 : CODE
     ( same as CREATE, but with native word )
     (entry)
-    ( JTBL+15 == next )
-    [ JTBL 15 + LITN ] ,
+    ( 23 == nativeWord )
+    23 ,
 ;
 
 : ;CODE JPNEXT, ;
 
 
 ( Routines )
-( JTBL+21 == next )
-: chkPS, [ JTBL 21 + LITN ] CALLnn, ;
+( 29 == chkPS )
+: chkPS, 29 CALLnn, ;

forth/z80c.fs

@@ -149,6 +149,19 @@ CODE XOR
     HL PUSHqq,
 ;CODE
 
+CODE NOT
+    HL POPqq,
+    chkPS,
+    A L LDrr,
+    H ORr,
+    HL 0 LDddnn,
+    3 JRNZe, ( skip)
+    ( false, make 1 )
+    HL INCss,
+( skip )
+    HL PUSHqq,
+;CODE
+
 CODE +
     HL POPqq,
     DE POPqq,
@@ -283,13 +296,13 @@ CODE J
 CODE >R
     HL POPqq,
     chkPS,
-    ( JTBL+9 == pushRS )
-    JTBL 9 + CALLnn,
+    ( 17 == pushRS )
+    17 CALLnn,
 ;CODE
 
 CODE R>
-    ( JTBL+12 == popRS )
-    JTBL 12 + CALLnn,
+    ( 20 == popRS )
+    20 CALLnn,
     HL PUSHqq,
 ;CODE
 
@@ -316,23 +329,23 @@ CODE BYE
 ;CODE
 
 CODE (resSP)
-    ( INITIAL_SP == JTBL+28 )
-    SP JTBL 28 + @ LDdd(nn),
+    ( INITIAL_SP == 36 )
+    SP 36 @ LDdd(nn),
 ;CODE
 
 CODE (resRS)
-    ( RS_ADDR == JTBL+38 )
-    IX JTBL 38 + @ LDddnn,
+    ( RS_ADDR == 46 )
+    IX 46 @ LDddnn,
 ;CODE
 
 CODE SCMP
     DE  POPqq,
     HL  POPqq,
     chkPS,
-    ( JTBL+35 == strcmp )
-    JTBL 35 + CALLnn,
-    ( JTBL+32 == flagsToBC )
-    JTBL 32 + CALLnn,
+    ( 43 == strcmp )
+    43 CALLnn,
+    ( 40 == flagsToBC )
+    40 CALLnn,
     BC PUSHqq,
 ;CODE
 
@@ -342,8 +355,58 @@ CODE CMP
     chkPS,
     A ORr,      ( clear carry )
     DE SBCHLss,
-    ( JTBL+32 == flagsToBC )
-    JTBL 32 + CALLnn,
+    ( 40 == flagsToBC )
+    40 CALLnn,
     BC PUSHqq,
 ;CODE
 
+CODE (parsed)
+    HL POPqq,
+    chkPS,
+    ( 60 == parseDecimal )
+    60 CALLnn,
+    10 JRZe, ( success )
+    ( error )
+    DE 0 LDddnn,
+    DE PUSHqq,  ( dummy )
+    DE PUSHqq,  ( flag )
+    JPNEXT,
+( success )
+    DE PUSHqq,
+    DE 1 LDddnn,
+    DE PUSHqq,
+;CODE
+
+CODE (find)
+    HL POPqq,
+    chkPS,
+    ( 3 == find )
+    3 CALLnn,
+    10 JRZe, ( found )
+    ( not found )
+    HL PUSHqq,
+    DE 0 LDddnn,
+    DE PUSHqq,
+    JPNEXT,
+( found )
+    DE PUSHqq,
+    DE 1 LDddnn,
+    DE PUSHqq,
+;CODE
+
+CODE SCPY
+    HL POPqq,
+    chkPS,
+    DE HERE LDdd(nn),
+    B 0 LDrn,
+( loop )
+    A (HL) LDrr,
+    LD(DE)A,
+    HL INCss,
+    DE INCss,
+    B INCr,
+    A ORr,
+    -6 JRNZe, ( loop )
+    DE A LD(dd)r
+    HERE DE LD(nn)dd,
+;CODE