Subversion Repositories bitserial

\
\ Cross Compiler and eForth interpreter for the bit-serial CPU available at:
\
\   <https://github.com/howerj/bit-serial>
\
\ This implements a Direct Threaded Code virtual machine on which we can
\ build a Forth interpreter.
\
\ References:
\
\ - <https://en.wikipedia.org/wiki/Threaded_code>
\ - <https://github.com/howerj/embed>
\ - <https://github.com/howerj/forth-cpu>
\ - <https://github.com/samawati/j1eforth>
\ - <https://www.bradrodriguez.com/papers/>
\ - 8086 eForth 1.0 by Bill Muench and C. H. Ting, 1990
\
\ The cross compiler has been tested and works with gforth versions 0.7.0 and
\ 0.7.3. An already compiled image (called 'bit.hex') should be available if
\ you do not have gforth installed.
\

only forth also definitions hex

wordlist constant meta.1
wordlist constant target.1
wordlist constant assembler.1
wordlist constant target.only.1

: (order) ( u wid*n n -- wid*n u n )
   dup if
    1- swap >r recurse over r@ xor if
     1+ r> -rot exit then r> drop then ;
: -order ( wid -- ) get-order (order) nip set-order ;
: +order ( wid -- ) dup >r -order get-order r> swap 1+ set-order ;

meta.1 +order also definitions

   2 constant =cell
4000 constant size ( 16384 bytes, 8192 cells )
2000 constant =end ( 8192  bytes, leaving 4096 for Dual Port Block RAM )
  40 constant =stksz
  60 constant =buf
0008 constant =bksp
000A constant =lf
000D constant =cr
007F constant =del

create tflash size cells here over erase allot

variable tdp
variable tep
variable tlast
size =cell - tep !
0 tlast !

: :m meta.1 +order also definitions : ;
: ;m postpone ; ; immediate
:m there tdp @ ;m
:m tc! tflash + c! ;m
:m tc@ tflash + c@ ;m
:m t! over ff and over tc! swap 8 rshift swap 1+ tc! ;m
:m t@ dup tc@ swap 1+ tc@ 8 lshift or ;m
:m talign there 1 and tdp +! ;m
:m tc, there tc! 1 tdp +! ;m
:m t, there t! 2 tdp +! ;m
:m $literal [char] " word count dup tc, 0 ?do count tc, loop drop talign ;m
:m tallot tdp +! ;m
:m thead
  talign
  there tlast @ t, tlast !
  parse-word dup tc, 0 ?do count tc, loop drop talign ;m
:m hex# ( u -- addr len )  0 <# base @ >r hex =lf hold # # # # r> base ! #> ;m
:m save-hex ( <name> -- )
  parse-word w/o create-file throw
  there 0 do i t@  over >r hex# r> write-file throw =cell +loop
   close-file throw ;m
:m save-target ( <name> -- )
  parse-word w/o create-file throw >r
   tflash there r@ write-file throw r> close-file ;m
:m .h base @ >r hex     u. r> base ! ;m
:m .d base @ >r decimal u. r> base ! ;m
:m twords
   cr tlast @
   begin
      dup tflash + =cell + count 1f and type space t@
   ?dup 0= until ;m
:m .stat
  0 if
    ." target: "      target.1      +order words cr cr
    ." target-only: " target.only.1 +order words cr cr
    ." assembler: "   assembler.1   +order words cr cr
    ." meta: "        meta.1        +order words cr cr
  then
  ." used> " there dup ." 0x" .h ." / " .d cr ;m
:m .end only forth also definitions decimal ;m
:m atlast tlast @ ;m
:m tvar   get-current >r meta.1 set-current create r> set-current there , t, does> @ ;m
:m label: get-current >r meta.1 set-current create r> set-current there ,    does> @ ;m
:m tdown =cell negate and ;m
:m tnfa =cell + ;m ( pwd -- nfa : move to name field address)
:m tcfa tnfa dup c@ $1F and + =cell + tdown ;m ( pwd -- cfa )
:m compile-only tlast @ tnfa t@ $20 or tlast @ tnfa t! ;m ( -- )
:m immediate    tlast @ tnfa t@ $40 or tlast @ tnfa t! ;m ( -- )
:m t' ' >body @ ;m
:m call 2/ C000 or ;m
:m t2/ 2/ ;m

: iOR      0000 or t, ;
: iAND     1000 or t, ;
: iXOR     2000 or t, ;
: iADD     3000 or t, ;
: iLSHIFT  4000 or t, ;
: iRSHIFT  5000 or t, ;
: iLOAD    2/ 6000 or t, ;
: iSTORE   2/ 7000 or t, ;

: iLOAD-C  2/ 8000 or t, ;
: iSTORE-C 2/ 9000 or t, ;
: iLITERAL A000 or t, ;
: iUNUSED  B000 or t, ;
: iJUMP    C000 or t, ;
: iJUMPZ   D000 or t, ;
: iSET     E000 or t, ;
: iGET     F000 or t, ;

 1 constant flgCy
 2 constant flgZ
 4 constant flgNg
 8 constant flgR
10 constant flgHlt

: flags? 1 iGET ;
: flags! 1 iSET ;
: halt!  flgHlt iLITERAL flags! ;
: branch  2/ iJUMP ;
: ?branch 2/ iJUMPZ ;
: zero? flags? 2 iAND ;
:m postpone t' branch ;m

assembler.1 +order also definitions
: begin there ;
: until ?branch ;
: again branch ;
: if there 0 ?branch ;
: mark there 0 branch ;
: then begin 2/ over t@ or swap t! ;
: else mark swap then ;
: while if swap ;
: repeat branch then ;
assembler.1 -order
meta.1 +order also definitions

\ ---- ---- ---- ---- ---- image generation   ---- ---- ---- ---- ---- ----

0 t,  \ must be 0 ('0 iOR'  works in either indirect or direct mode )
1 t,  \ must be 1 ('1 iADD' works in either indirect or direct mode )
2 t,  \ must be 2 ('2 iADD' works in either indirect or direct mode )
label: entry
0 t,  \ entry point to virtual machine

FFFF tvar set       \ all bits set, -1
  FF tvar low       \ lowest bytes set
   0 tvar <cold>    \ entry point of virtual machine program, set later on
   0 tvar pwd       \ previous word pointer

   0 tvar ip        \ instruction pointer
   0 tvar w         \ working pointer
   0 tvar t         \ temporary register
   0 tvar tos       \ top of stack
   0 tvar h         \ dictionary pointer
   0 tvar {state}   \ compiler state
   0 tvar {hld}     \ hold space pointer
   0 tvar {base}    \ input/output radix, default = 16
   0 tvar {dpl}     \ number of places after fraction
   0 tvar {in}      \ position in query string
   0 tvar {handler} \ throw/catch handler
   0 tvar {last}    \ last defined word
   0 tvar #tib      \ terminal input buffer

 =end                       dup tvar {sp0} tvar {sp} \ grows downwards
 =end =stksz 2* -           dup tvar {rp0} tvar {rp} \ grows upwards
 =end =stksz 2* - =buf - constant TERMBUF \ pad buffer space

TERMBUF =buf + constant =tbufend

: vcell 1 ( cell '1' should contain '1' ) ;
: -vcell set 2/ ;
: --sp {sp} iLOAD-C  vcell iADD {sp} iSTORE-C ;
: ++sp {sp} iLOAD-C -vcell iADD {sp} iSTORE-C ;
: --rp {rp} iLOAD-C -vcell iADD {rp} iSTORE-C ;
: ++rp {rp} iLOAD-C  vcell iADD {rp} iSTORE-C ;

\ ---- ---- ---- ---- ---- Forth VM ---- ---- ---- ---- ---- ---- ---- ----

label: start
  start call entry t!
  {sp0} iLOAD-C {sp} iSTORE-C
  {rp0} iLOAD-C {rp} iSTORE-C
  <cold> iLOAD-C
  ip iSTORE-C
  \ -- fall-through --
label: vm ( The Forth virtual machine )
  ip iLOAD-C
  w iSTORE-C
  ip iLOAD-C 1 iADD ip iSTORE-C
  w iLOAD-C
  0 iSET \ jump to next token

label: {nest} ( function call: accumulator must contain '0 iGET' prior to call )
  w iSTORE-C ( store '0 iGET' into working pointer )
  ++rp
  ip iLOAD-C
  {rp} iSTORE
  w iLOAD-C
  2 iADD
  ip iSTORE-C
  vm branch

label: {unnest} ( return from function call )
  {rp} iLOAD
  t iSTORE-C
  --rp
  t iLOAD-C
  ip iSTORE-C
  vm branch

:m nest 0 iGET {nest} branch ;m
:m unnest {unnest} branch ;m
:m =nest {nest} call ;m
:m =unnest {unnest} call ;m
:m =0iGET F000 ;m

:m :ht ( "name" -- : forth only routine )
  get-current >r target.1 set-current create
  r> set-current CAFEBABE talign there ,
  nest
  does> @ branch ( really a call ) ;m

:m :t ( "name" -- : forth only routine )
  >in @ thead >in !
  get-current >r target.1 set-current create
  r> set-current CAFEBABE talign there ,
  nest
  does> @ branch ( really a call ) ;m

:m :to ( "name" -- : forth only, target only routine )
  >in @ thead >in !
  get-current >r target.only.1 set-current create r> set-current
  there ,
  nest CAFEBABE
  does> @ branch ;m

:m ;t CAFEBABE <> if abort" unstructured" then talign unnest target.only.1 -order ;

:m a: ( "name" -- : assembly only routine, no header )
  CAFED00D
  target.1 +order also definitions
  create talign there ,
  assembler.1 +order
  does> @ branch ;m
:m (a); CAFED00D <> if abort" unstructured" then assembler.1 -order ;m
:m a; (a); vm branch ;m

label: IncIp ip iLOAD-C 1 iADD ip iSTORE-C vm branch
label: decSp tos iSTORE-C --sp vm branch

a: opPush ( pushes the next value in instruction stream on to the stack )
  ++sp
  tos iLOAD-C
  {sp} iSTORE
  ip iLOAD-C
  t iSTORE-C
  t iLOAD
  tos iSTORE-C
  IncIp branch
  (a);

a: opJump ( jump to next value in instruction stream )
label: Jump
  ip iLOAD
  ip iSTORE-C
  a;

a: opJumpZ
  tos iLOAD-C
  t iSTORE-C
  {sp} iLOAD
  tos iSTORE-C
  --sp
  t iLOAD-C
  if
    IncIp branch
  then
  Jump branch
  (a);

a: opNext
  {rp} iLOAD
  if
    set 2/ iADD
    {rp} iSTORE
    Jump branch
  then
  --rp
  IncIp branch
  (a);

:m lit         opPush t, ;m
:m [char] char opPush t, ;m
:m char   char opPush t, ;m
:m =push  [ t' opPush  ] literal call  ;m
:m =jump  [ t' opJump  ] literal call  ;m
:m =jumpz [ t' opJumpZ ] literal call  ;m
:m begin talign there ;m
:m until talign opJumpZ 2/ t, ;m
:m again talign opJump  2/ t, ;m
:m if opJumpZ there 0 t, ;m
:m mark opJump there 0 t, ;m
:m then there 2/ swap t! ;m
:m else mark swap then ;m
:m while if ;m
:m repeat swap again then ;m
:m aft drop mark begin swap ;m
:m next talign opNext 2/ t, ;m

a: bye halt! a;   ( -- : bye bye! )
a: exit unnest a; ( -- : exit from current function )

a: lls ( u shift -- u : shift left by number of bits set )
  {sp} iLOAD
  tos 2/ iLSHIFT
  decSp branch
  (a);

a: lrs ( u shift -- u : shift right by number of bits set )
  {sp} iLOAD
  tos 2/ iRSHIFT
  decSp branch
  (a);

a: and ( u u -- u : bit wise AND )
  {sp} iLOAD
  tos 2/ iAND
  decSp branch
  (a);

a: or ( u u -- u : bit wise OR )
  {sp} iLOAD
  tos 2/ iOR
  decSp branch
  (a);

a: xor ( u u -- u : bit wise XOR )
  {sp} iLOAD
  tos 2/ iXOR
  decSp branch
  (a);

a: + ( u u -- u : Plain old addition )
  {sp} iLOAD
  tos 2/ iADD
  decSp branch
  (a);

a: um+ ( u u -- u f : Add with carry )
  {sp} iLOAD
  tos 2/ iADD
  {sp} iSTORE
  flags?
  flgCy iAND
  tos iSTORE-C
  a;

a: @ ( a -- u : load a memory address )
  tos iLOAD-C
  1 iRSHIFT
  tos iSTORE-C
  tos iLOAD
  tos iSTORE-C
  a;

a: ! ( u a -- store a cell at a memory address )
  tos iLOAD-C
  1 iRSHIFT
  t iSTORE-C
  {sp} iLOAD
  t iSTORE
  --sp
  {sp} iLOAD
  decSp branch
  (a);

a: c@ ( b -- c )
  tos iLOAD-C
  1 iRSHIFT
  t iSTORE-C
  t iLOAD
  t iSTORE-C
  tos iLOAD-C
  1 iAND if
    t iLOAD-C
    low 2/ iRSHIFT
  else
    t iLOAD-C
    low 2/ iAND
  then
  tos iSTORE-C
  a;

a: dup ( u -- u u : duplicate item on top of stack )
  ++sp
  tos iLOAD-C
  {sp} iSTORE
  a;

a: drop ( u -- : drop it like it's hot )
  {sp} iLOAD
  decSp branch
  (a);

a: swap ( u1 u2 -- u2 u1 : swap top two stack items )
  {sp} iLOAD
  t iSTORE-C
  tos iLOAD-C
  {sp} iSTORE
  t iLOAD-C
  tos iSTORE-C
  a;

a: over ( u1 u2 -- u1 u2 u1 : reach over top of stack and copy next on stack )
  {sp} iLOAD
  t iSTORE-C
  ++sp
  tos iLOAD-C
  {sp} iSTORE
  t iLOAD-C
  tos iSTORE-C
  a;

a: 1- ( u -- u : decrement top of stack by one )
  tos iLOAD-C
  set 2/ iADD
  tos iSTORE-C
  a;

a: >r ( u -- , R: -- u : move variable from data to return stack )
  ++rp
  tos iLOAD-C
  {rp} iSTORE
  {sp} iLOAD
  decSp branch
  (a);

:m for talign >r begin ;m
:m =>r [ t' >r ] literal call ;m
:m =next [ t' opNext ] literal call ;m

a: r>  ( -- u , R: u -- : move variable from return to data stack )
  {rp} iLOAD
  t iSTORE-C
  --rp
  ++sp
  tos iLOAD-C
  {sp} iSTORE
  t iLOAD-C
  tos iSTORE-C
  a;

a: r@ ( -- u, R: u -- u : copy top of return stack to data stack )
  ++sp
  tos iLOAD-C
  {sp} iSTORE
  {rp} iLOAD
  tos iSTORE-C
  a;

a: rdrop ( --, R: u -- : drop top item on return stack )
  --rp
  a;

a: execute ( xt -- : execute an execution token! )
  tos iLOAD-C
  t iSTORE-C
  {sp} iLOAD
  tos iSTORE-C
  --sp
  t iLOAD-C
  1 iRSHIFT
  {nest} branch
  (a);

a: sp! ( ??? u -- ??? : set stack depth )
  tos iLOAD-C
  {sp} iSTORE-C
  {sp} iLOAD
  tos iSTORE-C
  a;

a: rp! ( u -- , R: ??? --- ??? : set return stack depth )
  tos iLOAD-C
  {rp} iSTORE-C
  {sp} iLOAD
  decSp branch
  (a);

a: sp@ ( -- u : get variable stack depth )
  {sp} iLOAD-C
  t iSTORE-C
  ++sp
  tos iLOAD-C
  {sp} iSTORE
  t iLOAD-C
  tos iSTORE-C
  a;

a: rp@ ( -- u : get return stack depth )
  ++sp
  tos iLOAD-C
  {sp} iSTORE
  {rp} iLOAD-C
  tos iSTORE-C
  a;

\ ---- ---- ---- ---- ---- no more direct assembly ---- ---- ---- ---- ----

assembler.1 -order

:ht #0   0 lit ;t ( --  0 : space saving measure, push  0 onto variable stack )
:ht #1   1 lit ;t ( --  1 : space saving measure, push  1 onto variable stack )
:ht #-1 -1 lit ;t ( -- -1 : space saving measure, push -1 onto variable stack )

\ Add words written in assembly into dictionary, you will need an understanding
\ of wordlists to understand this.

:to bye bye ;t
:to and and ;t
:to or or ;t
:to xor xor ;t
:to + + ;t
:to um+ um+ ;t
:to @ @ ;t
:to ! ! ;t
:to c@ c@ ;t
:to dup dup ;t
:to drop drop ;t
:to swap swap ;t
:to over over ;t
:to 1- 1- ;t
:to >r r> swap >r >r ;t compile-only
:to r> r> r> swap >r ;t compile-only
:to r@ r> r@ swap >r ;t compile-only
:to execute execute ;t

:t 0= if #0 exit then #-1 ;t
:t invert #-1 xor ;t
:t 1+ #1 + ;t
:t emit ( ch -- :  )
   begin 8002 lit @ 1000 lit and 0= until
   FF lit and 2000 lit or 8002 lit ! ;t
:t key? ( -- ch -1 | 0 )
   8002 lit @ 100 lit and if #0 exit then
   400 lit 8002 lit ! 8002 lit @ FF lit and #-1 ;t
:t here h lit @ ;t
:t base {base} lit ;t  ( -- a : base variable controls input/output radix )
:t dpl {dpl} lit ;t    ( -- a : push address of 'dpl' onto the variable stack )
:t hld {hld} lit ;t    ( -- a : push address of 'hld' onto the variable stack )
:t bl 20 lit ;t        ( -- space : push a space onto the stack )
:t >in {in} lit ;t     ( -- b : push pointer to terminal input position )
:t hex  $10 lit base ! ;t ( -- : switch to hexadecimal input/output radix )
:t source TERMBUF lit #tib lit @ ;t ( -- b u )
:t last {last} lit @ ;t      ( -- : last defined word )
:t state {state} lit ;t      ( -- a : compilation state variable )
:t ] #-1 state ! ;t          ( -- : turn compile mode on )
:t [ #0 state ! ;t immediate ( -- : turn compile mode off )
:t nip swap drop ;t          ( u1 u2 -- u2 : remove next stack value )
:t tuck swap over ;t         ( u1 u2 -- u2 u1 u2 : save top stack value )
:t ?dup dup if dup then ;t   ( u -- u u | 0 : duplicate if not zero )
:t rot >r swap r> swap ;t    ( u1 u2 u3 -- u2 u3 u1 : rotate three numbers )
:t 2drop drop drop ;t        ( u u -- : drop two numbers )
:t 2dup  over over ;t        ( u1 u2 -- u1 u2 u1 u2 : duplicate set of values )
:t +! tuck @ + swap ! ;t     ( n a -- : increment value at address by 'n' )
:t = xor 0= ;t               ( u u -- f : equality )
:t <> = 0= ;t                ( u u -- f : inequality )
:t 0>= 8000 lit and 0= ;t    ( n -- f : greater or equal to zero )
:t 0< 0>= 0= ;t              ( n -- f : less than zero )
:t negate 1- invert ;t       ( n -- n : negate [twos compliment] )
:t - negate + ;t             ( u u -- u : subtract )
:t < - 0< ;t                 ( n n -- f : signed less than )
:t > swap < ;t               ( n n -- f : signed greater than )
:t 0> #0 > ;t                ( n -- f : greater than zero )
:t 2* #1 lls ;t              ( u -- u : multiply by two )
:t 2/ #1 lrs ;t              ( u -- u : divide by two )
:t cell 2 lit ;t             ( -- u : size of memory cell )
:t cell+ cell + ;t           ( a -- a : increment address to next cell )
:t pick sp@ + 2* @ ;t        ( ??? u -- ??? u u : )
:t u< 2dup 0>= swap 0>= xor >r < r> xor ;t ( u u -- f : )
:t aligned dup #1 and + ;t       ( b -- u : align a pointer )
:t align here aligned h lit ! ;t ( -- : align dictionary pointer )
:t depth {sp0} lit @ sp@ - 1- ;t ( -- u : variable stack depth )
:t c! ( c b -- : store character at address )
  dup dup >r #1 and if
    @ 00FF lit and swap FF lit lls
  else
    @ FF00 lit and swap FF lit and
  then or r> ! ;t
:t count dup 1+ swap c@ ;t ( b -- b c : advance string, get next char )
:t allot aligned h lit +! ;t            ( u -- : allocate space in dictionary )
:t , align here ! cell allot ;t         ( u -- : write a value into the dictionary )
:t abs dup 0< if negate then ;t         ( n -- u : absolute value of a number )
:t mux dup >r and swap r> invert and or ;t ( u1 u2 f -- )
:t max 2dup < mux ;t  ( n n -- n : maximum of two numbers )
:t min 2dup > mux ;t  ( n n -- n : minimum of two numbers )
:t +string #1 over min rot over + rot rot - ;t ( b u -- b u : increment str )
:t catch ( xt -- exception# | 0 \ return addr on stack )
   sp@ >r              ( xt )   \ save data stack pointer
   {handler} lit @ >r  ( xt )   \ and previous handler
   rp@ {handler} lit ! ( xt )   \ set current handler
   execute             ( )      \ execute returns if no throw
   r> {handler} lit !  ( )      \ restore previous handler
   rdrop               ( )      \ discard saved stack ptr
   #0 ;t               ( 0 )    \ normal completion
:t throw ( ??? exception# -- ??? exception# )
    ?dup if              ( exc# )     \ 0 throw is no-op
      {handler} lit @ rp!   ( exc# )     \ restore prev return stack
      r> {handler} lit !    ( exc# )     \ restore prev handler
      r> swap >r            ( saved-sp ) \ exc# on return stack
      sp! drop r>           ( exc# )     \ restore stack
    then ;t
:t um* ( u u -- ud : double cell width multiply )
  #0 swap ( u1 0 u2 ) $F lit
  for dup um+ >r >r dup um+ r> + r>
    if >r over um+ r> + then
  next rot drop ;t
:t um/mod ( ud u -- ur uq : unsigned double cell width divide/modulo )
  ?dup 0= if -A lit throw then
  2dup u<
  if negate $F lit
    for >r dup um+ >r >r dup um+ r> + dup
      r> r@ swap >r um+ r> or
      if >r drop 1+ r> else drop then r>
    next
    drop swap exit
  then 2drop drop #-1 dup ;t
:t key begin key? until ;t     ( c -- : get a character from UART )
:t type begin dup while swap count emit swap 1- repeat 2drop ;t ( b u -- )
:t cmove for aft >r dup c@ r@ c! 1+ r> 1+ then next 2drop ;t ( b1 b2 u -- )
:t do$ r> r> 2* dup count + aligned 2/ >r swap >r ;t ( -- a : )
:t ($) do$ ;t            ( -- a : do string NB. )
:t .$ do$ count type ;t  ( -- : print string, next cells contain string )
:m ." .$ $literal ;m
:m $" ($) $literal ;m
:t space bl emit ;t               ( -- : print space )
:t cr .$ 2 tc, =cr tc, =lf tc, ;t ( -- : print new line )
:t ktap ( bot eot cur c -- bot eot cur )
  dup dup =cr lit <> >r  =lf lit <> r> and if \ Not End of Line?
    dup =bksp lit <> >r =del lit <> r> and if \ Not Delete Char?
      bl ( tap -> ) dup emit over c! 1+ ( bot eot cur c -- bot eot cur )
      exit
    then
    >r over r@ < dup if
      =bksp lit dup emit space emit
    then
    r> +
    exit
  then drop nip dup ;t
:t accept ( b u -- b u : read in a line of user input )
  over + over
  begin
    2dup xor
  while
    key dup bl - $5F lit u< if ( tap -> ) dup emit over c! 1+ else ktap then
  repeat drop over - ;t
:t query TERMBUF lit =buf lit accept #tib lit ! drop #0 >in ! ;t ( -- : get line)
:t ?depth depth > if -4 lit throw then ;t ( u -- : check stack depth )
:t -trailing ( b u -- b u : remove trailing spaces )
  for
    aft bl over r@ + c@ <
      if r> 1+ exit then
    then
  next #0 ;t
:ht look ( b u c xt -- b u : skip until *xt* test succeeds )
  swap >r rot rot
  begin
    dup
  while
    over c@ r@ - r@ bl = 4 lit pick execute
    if rdrop rot drop exit then
    +string
  repeat rdrop rot drop ;t
:ht no-match if 0> exit then 0= 0= ;t ( c1 c2 -- t )
:ht match no-match invert ;t          ( c1 c2 -- t )
:t parse ( c -- b u ; <string> )
    >r source drop >in @ + #tib lit @ >in @ - r@
    >r over r> swap >r >r
    r@ t' no-match lit look 2dup
    r> t' match    lit look swap r> - >r - r> 1+  ( b u c -- b u delta )
    >in +!
    r> bl = if -trailing then #0 max ;t
:t spaces begin dup 0> while space 1- repeat drop ;t ( +n -- )
:t hold #-1 hld +! hld @ c! ;t ( c -- : save a character in hold space )
:t #> 2drop hld @ =tbufend lit over - ;t  ( u -- b u )
:t #  ( d -- d : add next character in number to hold space )
   2 lit ?depth
   #0 base @
   ( extract ->) dup >r um/mod r> swap >r um/mod r> rot ( ud ud -- ud u )
   ( digit -> ) 9 lit over < 7 lit and + [char] 0 + ( u -- c )
   hold ;t
:t #s begin # 2dup ( d0= -> ) or 0= until ;t       ( d -- 0 )
:t <# =tbufend lit hld ! ;t                        ( -- )
:t sign 0< if [char] - hold then ;t                ( n -- )
:t u.r >r #0 <# #s #>  r> over - spaces type ;t    ( u +n -- : print u right justified by +n )
:t u.  #0 <# #s #> space type ;t                   ( u -- : print unsigned number )
:t . dup >r abs #0 <# #s r> sign #> space type ;t  ( n -- print number )
:t >number ( ud b u -- ud b u : convert string to number )
  begin
    2dup >r >r drop c@ base @        ( get next character )
    ( digit? -> ) >r [char] 0 - 9 lit over <
    if 7 lit - dup $A lit < or then dup r> u< ( c base -- u f )
    0= if                            ( d char )
      drop                           ( d char -- d )
      r> r>                          ( restore string )
      exit                           ( ..exit )
    then                             ( d char )
    swap base @ um* drop rot base @ um* ( d+ -> ) >r swap >r um+ r> + r> + ( accumulate digit )
    r> r>                            ( restore string )
    +string dup 0=                   ( advance string and test for end )
  until ;t
:t number? ( a u -- d -1 | a u 0 : string to a number [easier to use] )
  #-1 dpl !
  base @ >r
  over c@ [char] - = dup >r if     +string then
  over c@ [char] $ =        if hex +string then
  >r >r #0 dup r> r>
  begin
    >number dup
  while over c@ [char] . xor
    if rot drop rot r> 2drop #0 r> base ! exit then
    1- dpl ! 1+ dpl @
  repeat 
  2drop r> if 
    ( dnegate -> ) invert >r invert #1 um+ r> + 
  then r> base ! #-1 ;t
:t compare ( a1 u1 a2 u2 -- n : string equality )
  rot
  over - ?dup if >r 2drop r> nip exit then
  for ( a1 a2 )
    aft
      count rot count rot - ?dup
      if rdrop nip nip exit then
    then
  next 2drop #0 ;t
:to .s depth  for aft r@ pick . then next ;t ( -- : print variable stack )
:t nfa cell+ ;t ( pwd -- nfa : move word pointer to name field )
:t cfa nfa dup c@ $1F lit and + cell+ cell negate and ;t ( pwd -- cfa )
:t (find) ( a wid -- PWD PWD 1|PWD PWD -1|0 a 0: find word in WID )
  swap >r dup
  begin
    dup
  while
    dup nfa count $9F lit ( $1F:word-length + $80:hidden ) and r@ count compare 0=
    if ( found! )
      rdrop
      dup ( immediate? -> ) nfa $40 lit swap @ and 0= 0=
      #1 or negate exit
    then
    nip dup @
  repeat
  2drop #0 r> #0 ;t
:t find last (find) rot drop ;t  ( "name" -- b )
:t literal state @ if =push lit , , then ;t immediate ( u -- )
:t compile, 2/ align C000 lit or , ;t                 ( xt -- )
:t ?found if exit then space count type [char] ? emit cr -D lit throw ;t ( u f -- )
:t interpret                                          ( b -- )
  find ?dup if
    state @
    if
      0> if cfa execute exit then \ <- immediate word are executed
      cfa compile, exit           \ <- compiling word are...compiled.
    then
    drop
    dup nfa c@ 20 lit and if -E lit throw then ( <- ?compile )
    cfa execute exit  \ <- if its not, execute it, then exit *interpreter*
  then
  \ not a word
  dup >r count number? if rdrop \ it is a number!
    dpl @ 0< if \ <- dpl will be -1 if it is a single cell number
       drop     \ drop high cell from 'number?' for single cell output
    else        \ <- dpl is not -1, it is a double cell number
       state @ if swap then
       postpone literal \ literal is executed twice if it's a double
    then
    postpone literal exit
  then
  r> #0 ?found \ Could vector ?found here, to handle arbitrary words
  ;t
:t word parse here dup >r 2dup ! 1+ swap cmove r> ;t ( c -- b )
:to words last begin dup nfa count 1f lit and space type @ ?dup 0= until ;t
:to see bl word find ?found
    cr begin dup @ =unnest lit <> while dup @ u. cell+ repeat @ u. ;t
:to : align here last , {last} lit ! ( "name" -- : define a new word )
    bl word
    dup c@ 0= if -A lit throw then
    count + h lit ! align
    =0iGET lit , =nest lit , ] BABE lit ;t
:to ; postpone [ BABE lit <> if -16 lit throw then  =unnest lit , ;t immediate compile-only
:to begin align here ;t immediate compile-only
:to until =jumpz lit , 2/ , ;t immediate compile-only
:to again =jump  lit , 2/ , ;t immediate compile-only
:to if =jumpz lit , here #0 , ;t immediate compile-only
:to then here 2/ swap ! ;t immediate compile-only
:to for =>r lit , here ;t immediate compile-only
:to next =next lit , 2/ , ;t immediate compile-only
:to ' bl word find ?found cfa literal ;t immediate
:t compile r> dup 2* @ , 1+ >r ;t compile-only ( -- : compile next compiled into dictionary )
:to exit compile exit ;t immediate compile-only
:to ." compile .$  [char] " word count + h lit ! align ;t immediate compile-only
:to $" compile ($) [char] " word count + h lit ! align ;t immediate compile-only  \ "
:to ( [char] ) parse 2drop ;t immediate ( "comment" -- discard until parenthesis )
:to \ source drop @ >in ! ;t immediate  ( "comment" -- discard until end of line )
:to immediate last nfa @ $40 lit or last nfa ! ;t ( -- : turn previously defined word into an immediate one )
:to dump begin over c@ u. +string ?dup 0= until drop ;t
:t eval begin bl word dup c@ while interpret #1 ?depth repeat drop ."  ok" cr ;t ( "word" -- )
:t ini hex postpone [ #0 >in ! #-1 dpl ! ;t ( -- )
:t quit ( -- : interpreter loop [and more, does more than most QUITs] )
   there t2/ <cold> t! \ program entry point set here
   ." eForth 3.2" cr
   ini 
   begin
     query t' eval lit catch
     ( ?error -> ) ?dup if
       space . [char] ? emit cr ini
     then again ;t

\ ---- ---- ---- ---- ---- implementation finished ---- ---- ---- ---- ----

there h t!
atlast {last} t!
save-hex bit.hex
save-target bit.bin
.stat
.end
.( DONE ) cr
bye