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planckforth/core.fs
Koichi Nakamura 4f2581968d Add "immediate"
2021-01-01 08:23:45 +09:00

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h@l@h@!h@C+h!k1k0-h@$k
h@k1k0-+$h@C+h!ih@!h@C+h!kefh@!h@C+h!l!
h@l@h@!h@C+h!k1k0-h@$k h@k1k0-+$h@C+h!ih@!h@C+h!kefh@!h@C+h!l!
h@l@ h@!h@C+h! k1k0-h@$ k\h@k1k0-+$ h@C+h!
i h@!h@C+h!
kkf h@!h@C+h!
kLf h@!h@C+h!
k:k0- h@!h@C+h!
k=f h@!h@C+h!
kJf h@!h@C+h!
k0k5-C* h@!h@C+h!
kef h@!h@C+h!
l!
\ **Now we can use single-line comments!**
\ planckforth -
\ Copyright (C) 2020 nineties
\ This project aims to create a full-fledged Forth interpreter
\ by bootstrapping from hand-written tiny ELF binary.
\ In the 1st stage, only single character words are registered
\ in the dictionary.
\ List of builtin words:
\ 'Q' ( -- ) Exit the process
\ 'C' ( -- n ) The size of Cells
\ 'h' ( -- addr ) The address of 'here' cell
\ 'l' ( -- addr ) The address of 'latest' cell
\ 'k' ( -- c ) Read character
\ 't' ( c -- ) Print character
\ 'j' ( -- ) Unconditional branch
\ 'J' ( a -- ) Jump if a == 0
\ 'f' ( c -- xt ) Get execution token of c
\ 'x' ( xt -- ... ) Run the execution token
\ '@' ( addr -- a ) Load value from addr
\ '!' ( a addr -- ) Store value to addr
\ '?' ( addr -- c ) Load byte from addr
\ '$' ( c addr -- ) Store byte to addr
\ 'd' ( -- addr ) Get data stack pointer
\ 'D' ( addr -- ) Set data stack pointer
\ 'r' ( -- addr ) Get return stack pointer
\ 'R' ( addr -- ) Set return stack pointer
\ 'i' ( -- addr ) Get the interpreter function
\ 'e' ( -- ) Exit current function
\ 'L' ( -- a ) Load immediate
\ 'S' ( -- addr len) Load string literal
\ '+' ( a b -- c ) c = (a + b)
\ '-' ( a b -- c ) c = (a - b)
\ '*' ( a b -- c ) c = (a * b)
\ '/' ( a b -- c ) c = (a / b)
\ '%' ( a b -- c ) c = (a % b)
\ '&' ( a b -- c ) c = (a & b)
\ '|' ( a b -- c ) c = (a | b)
\ '^' ( a b -- c ) c = (a ^ b)
\ '<' ( a b -- c ) c = (a < b)
\ '=' ( a b -- c ) c = (a == b
\ The 1st stage interpreter repeats execution of k, f and x.
\ There is no concept such as IMMEDIATE mode yet.
\ There following line is an example program of planckforth
\ which prints "Hello World!\n"
\ --
\ kHtketkltkltkotk tkWtkotkrtkltkdtk!tk:k0-tQ
\ --
\ This code repeats that 'k' reads a character and 't' prints it.
\ Note that ':' (58) minus '0' (48) is '\n' (10).
\ The structure of the dictionary is sames as many Forth implementation.
\ +------+----------+---------+------------+---------------+
\ | link | len+flag | name... | padding... | code field ...|
\ +------+----------+---------+------------+---------------+
\ - link pointer to the previous entry (CELL byte)
\ - length of the name (7 bits)
\ - immediate flag (1 bit)
\ - characters of the name (N bits)
\ - padding to align CELL boundary if necessary.
\ - codewords and datawords (CELL-bye aligned)
\ The code group at the beginning of this file
\ defines ' ' and '\n' as no-op operation and
\ '\' to read following characters until '\n'.
\ Since I couldn't write a comment at the beginning,
\ I repost the definition of '\' for explanation.
\ --
\ h@ ( save addr of new entry )
\ l@ h@!h@C+h! ( set link pointer. *here++ = latest )
\ k1k0-h@$ k\h@k1k0-+$ h@C+h! ( write the name '\' and its length )
\ i h@!h@C+h! ( docol )
\ kkf h@!h@C+h! ( key )
\ kLf h@!h@C+h! ( lit )
\ k:k0- h@!h@C+h! ( '\n' )
\ k=f h@!h@C+h! ( = )
\ kJf h@!h@C+h! ( branch )
\ k0k5-C* h@!h@C+h! ( -5*CELL )
\ kef h@!h@C+h! ( exit )
\ l! ( set latest to this new entry. )
\ --
\ That's all for the brief explanation. Let's restart bootstrap!
\ The COMMA operator
\ ',' ( a -- ) Store a to 'here' and increment 'here' CELL bytes.
h@l@ h@!h@C+h! k1k0-h@$ k,h@k1k0-+$ h@C+h!
i h@!h@C+h! \ docol
\ store 'a' to here
khf h@!h@C+h!
k@f h@!h@C+h!
k!f h@!h@C+h!
\ here <- here + CELL
khf h@!h@C+h!
k@f h@!h@C+h!
kCf h@!h@C+h!
k+f h@!h@C+h!
khf h@!h@C+h!
k!f h@!h@C+h!
\ exit
kef h@!h@C+h!
l!
\ TICK-like operator
\ '\'' ( "c" -- xt ) Get execution token of following character
\ NB: This definition is different from the usual definition of tick
\ because it does not skip leading spaces and can read only a single
\ character. It will be redefined in later stage.
h@l@, k1k0-h@$ k'h@k1k0-+$ h@C+h!
i, kkf, kff, kef,
l!
\ Utility for defining a word
\ 'c' ( "c" -- w )
\ Read character, create new word then push its address.
\ 'latest' will not be updated.
h@l@, k1k0-h@$ kch@k1k0-+$ h@C+h!
i, 'h, '@, 'l, '@, ',,
'L, k1k0-, 'h, '@, '$,
'k, 'h, '@, 'L, k1k0-, '+, '$,
'h, '@, 'C, '+, 'h, '!,
'e, l!
\ '_' ( a -- ) DROP
c_ i, 'd, 'C, '+, 'D, 'e, l!
\ '#' ( a -- a a ) DUP
c# i, 'd, '@, 'e, l!
\ Implementations of TOR and FROMR are a bit tricky.
\ Since return-address will be placed at the top of return stack,
\ the code in the body of these function have to manipulate
\ 2nd element of the stack.
\ '{' ( a -- R:a ) TOR
\ Move value from data stack to return stack.
c{ i,
'r, 'r, '@, \ ( a rsp ret )
'r, 'C, '-, '#, \ ( a rsp ret rsp-1 rsp-1 )
'R, \ ( a rsp+1 ret rsp ) extend return stack
'!, \ ( a rsp+1 ) store return address to the top
'!, \ store a to the 2nd
'e, l!
\ '}' ( R:a -- a ) FROMR
\ Move value from return stack to data stack.
c} i,
'r, 'C, '+, '@, \ ( a ) load 2nd value
'r, '@, \ ( a ret ) load return addr
'r, 'C, '+, '#, \ ( a ret rsp+1 rsp+1 )
'R, \ ( a ret rsp ) reduce return stack
'!, \ ( a , R:ret ) store return addr to top of return stack
'e, l!
\ 'o' ( a b -- a b a ) OVER
co i, 'd, 'C, '+, '@, 'e, l!
\ '~' ( a b -- b a ) SWAP
c~ i,
'o, \ ( a b a )
'{, \ ( a b , R:a )
'd, 'C, '+, \ ( a b sp+1 , R:a )
'!, \ ( b , R:a )
'}, \ ( b a )
'e, l!
\ 'B' ( c -- ) C-COMMA
\ Store byte 'c' to here and increment it
cB i, 'h, '@, '$, 'h, '@, 'L, k1k0-, '+, 'h, '!, 'e, l!
\ 'm' ( c-addr u -- ) CMOVE,
\ Copy u bytes from c-addr to here,
\ increment here u bytes.
cm i,
\ <loop>
'#, 'J, k>k0-C*, \ goto <exit> if u=0
'{, \ preserve u
'#, '?, 'B, \ copy byte
'L, k1k0-, '+, \ increment c-addr
'}, 'L, k1k0-, '-, \ decrement u
'j, k0k?-C*, \ goto <loop>
\ <exit>
'_, '_,
'e, l!
\ 'a' ( c-addr -- a-addr ) ALIGNED
\ Round up to a nearlest multiple of CELL
ca i,
'L, Ck1k0--, '+, \ ( a+CELL-1 )
'L, k0k0-C-, \ ( a+CELL-1 ~(CELL-1) )
'&,
'e, l!
\ 'A' ( -- ) ALIGN
\ Round up 'here' to a nearlest multiple of CELL
cA i, 'h, '@, 'a, 'h, '!, 'e, l!
\ 'E' ( c-addr1 u1 c-addr2 u2 -- n ) STR=
\ Compare two strings.
\ Return 1 if they are same 0 otherwise.
cE i,
'{, '~, '}, \ ( c-addr1 c-addr2 u1 u2 )
'o, '=, 'J, kVk0-C*, \ jump to <not_equal> if u1!=u2
\ <loop>
\ ( c-addr1 c-addr2 u )
'#, 'J, kMk0-C*, \ jump to <equal> if u==0
'{, \ preserve u
'o, '?, \ ( c-addr1 c-addr2 c1 )
'o, '?, \ ( c-addr1 c-addr2 c1 c2 )
'}, \ ( c-addr1 c-addr2 c1 c2 u ) restore u
'~, '{, '~, '}, \ ( c-addr1 c-addr2 u c1 c2 )
'=, 'J, kFk0-C*, \ jump to <not_equal> if c1!=c2
'{, '{, \ ( c-addr1 , R:u c-addr2 )
'L, k1k0-, '+, \ increment c-addr1
'}, 'L, k1k0-, '+, \ increment c-addrr2
'}, 'L, k1k0-, '-, \ decrement u
'j, k0kN-C*, \ jump to <loop>
\ <equal>
'_, '_, '_, 'L, k1k0-, 'e,
\ <not_equal>
'_, '_, '_, 'L, k0k0-, 'e,
l!
\ 's' ( c -- n)
\ Return 1 if c==' ' or c=='\n', 0 otherwise.
cs i, '#, 'L, k , '=, '~, 'L, k:k0-, '=, '|, 'e, l!
\ 'W' ( "name" -- c-addr u )
\ Skip leading spaces (' ' and '\n'),
\ Read name, then return its address and length.
\ The maximum length of the name is 127. The behavior is undefined
\ when the name exceeds 127 characters,
\ Note that it returns the address of statically allocated buffer,
\ so the content will be overwritten each time 'w' executed.
\ Allocate buffer of 127 bytes or more,
\ push the address for compilation of 'w'
h@ # kOk0++ h! A
cW~
i,
\ skip leading spaces
'k, '#, 's, 'J, k4k0-C*, '_, 'j, k0k7-C*,
\ p=address of buffer
'L, #, '~,
\ <loop>
\ ( p c )
'o, '$, \ store c to p
'L, k1k0-, '+, \ increment p
'k, '#, 's, 'J, k0k9-C*, \ goto <loop> if c is not space
'_, 'L, , \ ( p buf )
'~, 'o, '-, \ ( buf p-buf )
'e, l!
\ 'F' ( c-addr u -- w )
\ Lookup multi-character word from dictionary.
\ Return 0 if the word is not found.
cF i,
'l, '@,
\ <loop> ( addr u it )
'#, 'J, kIk0-C*, \ goto <exit> if it=NULL
'{, 'o, 'o, 'r, '@, '~, '{, '~, '}, '},
\ ( addr u it addr u it )
'#, 'L, Ck1k0-+, '+, \ address of name
'~, 'C, '+, '?, \ length+flag
'L, kOk0+, '&, \ take length (lower 7-bits)
\ ( addr1 u1 it addr1 u1 addr2 u2 )
'E, 'J, k3k0-C*, \ goto <1> if different name
'j, k4k0-C*, \ goto <exit>
\ <1>
'@, 'j, k0kO-C*, \ load link, goto <loop>
\ <exit>
'{, '_, '_, '}, \ Drop addr u return it
'e, l!
\ 'G' ( w -- xt )
\ Get CFA of the word
cG i,
'C, '+, '#, '?, \ ( addr len+flag )
'L, kOk0+, '&, \ take length
'+, \ add length to the addr
'L, k1k0-, '+, \ add 1 to the addr (1byte for len+field)
'a, \ align
'e, l!
\ 'M' ( -- c-addr)
\ The state variable
\ 0: immediate mode
\ 1: compile mode
h@ k0k0-, \ allocate 1 cell and fill 0
cM~ i, 'L, , 'e, l!
\ 'I'
\ The 2nd Stage Interpreter
cI i,
\ <loop>
'W, \ read name from input
'F, \ find word
'M, '@, \ read state
'J, kAk0-C*, \ goto <immediate> if state=0
\ <compile>
'#, 'C, '+, '?, \ ( w len+flag )
'L, k@k@+, '&, \ test immediate bit
'L, k0k0-, '=,
'J, k5k0-C*, \ goto <immediate> if immediate-bit=1
'G, ',, \ compile CFA
'j, k0kE-C*, \ goto <loop>
\ <immediate>
'G, 'x, \ execute CFA
'j, k0kI-C*, \ goto <loop>
l!
I \ Enter 2nd Stage
\ === 2nd Stage Interpreter ===
r C + R \ Drop 1st stage interpreter from call stack
\ '\'' ( "name" -- xt )
\ Redefine existing '\'' which uses 'k' and 'f'
\ to use 'W' and 'F'.
c ' i , ' W , ' F , ' G , ' e , l !
\ [ immediate ( -- )
\ Switch to immediate mode
c [ i , ' L , k 0 k 0 - , ' M , ' ! , ' e , l !
\ Set immediate-bit of [
l @ C + # { ? k @ k @ + | } $
\ ] ( -- )
\ Switch to compile mode
c ] i , ' L , k 1 k 0 - , ' M , ' ! , ' e , l !
\ : ( "name" -- R:w ) COLON
\ Read name, create word, push it to return stack,
\ compile 'docol' and enter compile mode.
c : i ,
\ save the address of the word to
\ **2nd position** of return stack.
\ Same reasons for TOR and FROMR
' h , ' @ ,
' } , ' ~ , ' { , ' { ,
' l , ' @ , ' , , \ fill link
' W , \ read name ( addr len )
' # , ' B , \ fill length ( addr len )
' m , \ fill name
' A , \ align here
' i , ' , , \ compile docol
' ] , \ enter compile mode
' e , l !
\ ; immediate ( R:w -- ) SEMICOLON
\ Compile 'exit', add w to dictionary and enter immediate mode.
c ; i ,
' L , ' e , ' , , \ compile exit
\ pick 2nd element of return stack
' } , ' } , ' ~ , ' { ,
' l , ' ! , \ update latest
' [ , \ enter immediate mode
' e , l !
\ Set immediate-bit of ';'
l @ C + # { ? k @ k @ + | } $
: immediate-bit [ ' L , k @ k @ + , ] ;
: length-mask [ ' L , k O k 0 + , ] ;
\ ( "name" -- )
: set-immediate
W F C + # { ? immediate-bit | } $
;
\ Set immediate-bit of single-line comment word \
\ so that we can write comments in compile-mode.
set-immediate \
\ Set immediate-bit of the word being defind
: immediate
r @ C + # { ? immediate-bit | } $
;
set-immediate immediate
: alias-builtin \ ( "name-new" "name-old" -- )
\ Create new word "name-new".
\ Copy code pointer of builtin word "name-old" to
\ the new word "name-new".
\ "name-old" must not be a FORTH word.
h @ l @ , l ! \ fill link, update latest
W # B m A \ fill length and chars of "name-new"
W F G @ , \ fill code-pointer of "name-old"
;
\ Add new names to builtin primities.
\ Instead of defining as a new FORTH word like shown below,
\ the aliases ared created by copying their code-pointer.
\ : new-name old-name ;
\ Primitive operators which manipulate program counter and return stack
\ can not be defined as a FORTH word.
alias-builtin bye Q
alias-builtin cell C
alias-builtin here h
alias-builtin latest l
alias-builtin key k
alias-builtin emit t
alias-builtin branch j
alias-builtin 0branch J
alias-builtin execute x
alias-builtin c@ ?
alias-builtin c! $
alias-builtin sp@ d
alias-builtin sp! D
alias-builtin rp@ r
alias-builtin rp! R
alias-builtin docol i
alias-builtin exit e
alias-builtin lit L
alias-builtin litstring S
alias-builtin div /
alias-builtin mod %
alias-builtin and &
alias-builtin or |
alias-builtin xor ^
bye
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