CamelForth
Resources
- CamelForth Z80
- On RC2014 Picasso (Minit II) ROM it is available in 8 KiB Bank 8 (JP:
0001). - Forth Tutorials
Basics
gforth are case-insensitive, CamelForth is case-sensitive.
There are two operation modes:
>R and R>).
The interpreter treats any number as literal to be put on stack and any word as call to a word - these are space separated.
There are special cases for words that switch into compiled mode (:, CREATE) that take a word as argument following it; also ' to get address of the word without calling its action - word address on stack can be executed with EXECUTE.
Each word consist of a link to previously defined word, name, storage area and action code:
CREATE or :.
When word name is called its parameter filed address is placed on the stack and associated action code (new thread) is jumped to.
When using CREATE data can be stored under address of word using !, a buffer of cells or bytes can be allocated using ALLOT. , can be used to append cells to last created word.
Action code can be appended to word using : or CREATE and appending DOES>.
CamelForth adds NEXT to each word implementation to load next word to be interpreted and jump to its implementation. After word definition is executed, EXIT is called that pops return address from return stack and jumps to it with NEXT. EXECUTE pops address of word from stack and jumps to it. DOES> will then put old interpreter pointer on return stack and load new pointer and parameter field address from parameter stack and put parameter field address as top of stack, then call NEXT. This way CamelForth does not use function call instructions but does use SP register and pop/push to manipulate parameter stack.
Comments
- *not supported in CamelForth *
\(back slash) comment to the end of line. (and)to comment inline.
Stack manipulation
1 2 3 ( put 1 2 and 3 on stack )
. ( pip from stack and dispaly )
.S ( show stack (gfort) )
2 DUP ( duplicate: 2 2 )
1 2 SWAP ( swap 2 items: 2 1 )
1 2 OVER ( copy secondmost item to top: 1 2 1 )
1 2 DROP ( drop top item: 1 )
1 2 3 ROT ( move thirdmost item to top: 2 3 1 )
1 2 NIP ( drop secondmost: 2 )
1 2 TUCK ( dup top before secondmost: 2 1 2 )
Return stack
Word calls put address in return stack and ; is compiled as EXIT that pops it and jump to it. It is also used by loops to keep track of condition variables and iterators and value for I.
>Rpops data stack value on return stack.R>pops return stack value to data stack.R@duplicates returns stack value to data stack.
These can be used to temporary store values on return stack but it has to be balanced and may mess with I and loop data if used inside loops.
Note that these only work in compiled context.
Arithmetic
1 2 3 4 + - * ( 3+4=7, 2-7=-5, 1*-5=-5 )
Note that CamelForth .S displays signed integers, . will print correct result.
Defining words
: DUBL 2 * ; ( define DUBL word that puts 2 on stack and multiplies two stack items )
3 DUBL ( now can be called like any other word: 6 )
Printing strings
Strings are put on stack as pair of address and length.
: FOO S" Hello HxD" ( record string on stack )
TYPE ; ( print the string )
FOO
Note that in CamelForth S" can only be used in compiled context.
Introspection
WORDS ( list defined words )
Variables
Variables are words, calling vairable puts its address on stack.
VARIABLE blah ( define variable word )
42 blah ! ( store 42 in blah variable )
blah @ ( put value on stack )
blah ? ( read and print variable )
5 CONSTANT five ( declare constant )
five SPACES ( print 5 spaces )
In Forth ture is -1 and false is 0. CamelForth does not have TRUE and FALSE words defined.
Control flow
IF checks result on top of the stack (-1 - true, 0 - false). then is end of if.
VARIABLE var
4 var !
: test var @ 5 >
IF ." Greater" CR
ELSE ." Less or equal" CR
THEN ;
test
- not available in CamelForth
?DOtakes end and start value andLOOPcalls next iteration or is end of loop. DOiterates always once.Iin context of iteration puts iteration count on the stack.2 +loopwill step by 2 while-1 +loopwill count down.leavebreaks the loop.
: test 11 1 DO I . CR LOOP ;
test
: fib 0 1
BEGIN
DUP >R ROT DUP R> > ( condition )
WHILE
ROT ROT DUP ROT + DUP . ( body )
REPEAT
DROP DROP DROP ; ( after loop has executed )
20 fib
: lcd
BEGIN
SWAP OVER MOD ( body )
DUP 0= ( condition )
UNTIL DROP . ;
27 21 lcd ( 3 )
Infinite loop.
: test BEGIN ." Diamonds are forever" CR AGAIN ;
Arrays
Access works by adding offset of size cells to base array address and then accessing via it like normal variable.
CREATE foo 16 CELLS ALLOT ( creates array foo with 16 elements )
5 foo 2 CELLS + ! ( store 5 in index 2 )
4 foo ! ( store 4 in index 1 )
foo 2 CELLS + @ ( put value at index 2 on stack )
foo @ ( put value at index 1 on stack )
Constants are added with , word.
CREATE SIZES 18 , 21 , 24 , 27 , 30 , 255 ,
Strings
Have two forms:
- Address and length - consumed by
TYPE, - Counted string -
ALLOCallocated address where first byte is string length and rest is the string itself.
S"creates string constant. It can be copied to an allocated buffer withCMOVE.COUNTcan be used to get count from counted string.CHAR+orCHARSadds character(s) worth of bytes to address.
: test S" hello bar" TYPE ; ( puts address and length on stack and print it out )
CREATE foo 16 CHARS ALLOT ( allocate 16 character long buffer )
: hello S" Hello World!" ; ( put "Hello World!" )
hello ( put address and length to "Hello World!" word )
foo ! ( store string lenght in first byte - c-addr )
foo COUNT ( get the length and first byte address -c-addr c-addr u )
CMOVE ( copy string from contant to the buffer+1 )
foo COUNT TYPE ( print counted string )
On CamelForth foo COUNT looks like it gives wrong address but if one prints it with . it shows negative
number that is actually 1 more than foo so it is correct.
Place constant string in variable buffer.
: PLACE TUCK ! COUNT CMOVE ;
CREATE bar 16 CHARS ALLOT
: hello S" Hello World!" ; ( put "Hello World!" )
hello bar PLACE ( store "Hello World!" in bar )
bar COUNT
TYPE ( print "Hello World!" from counted string variable bar )
Note that CamelForth has non-standard >COUNTED that does what PLACE does.
Pointers
: goodbye ." Goodbye" CR ;
: hello ." Hello" CR ;
VARIABLE a
: GREET a @ EXECUTE ;
' hello a !
GREET
' goodbye a !
GREET
'puts address of following word on stack without executing it.EXECUTEexecute word from address on stack.
Meta words
: displaynumber CREATE , DOES> @ . ;
11 displaynumber anumber
anumber
CREATEtakes a name (as inCREATE foo), in this caseCREATE anumber, and creates an empty word for that name.,appends to the created word (storage) a cell from stack (11)- When calling created word (just
anumber) it puts its address on the stack,@can read cell behind that address (11). DOES>will attach anacctionaction to the word that executes when word is called (justanumber) and after its address is put on stack. In this example we read value from that words address (11) and print it with..
CamelForth Words
Low level
TABLE 1. GLOSSARY OF WORDS IN CAMEL80.AZM
Words which are (usually) written in CODE.
NAME stack in -- stack out description
Guide to stack diagrams: R: = return stack,
c = 8-bit character, flag = boolean (0 or -1),
n = signed 16-bit, u = unsigned 16-bit,
d = signed 32-bit, ud = unsigned 32-bit,
+n = unsigned 15-bit, x = any cell value,
i*x j*x = any number of cell values,
a-addr = aligned adrs, c-addr = character adrs
p-addr = I/O port adrs, sys = system-specific.
Refer to ANS Forth document for more details.
ANS Forth Core words
These are required words whose definitions are
specified by the ANS Forth document.
! x a-addr -- store cell in memory
+ n1/u1 n2/u2 -- n3/u3 add n1+n2
+! n/u a-addr -- add cell to memory
- n1/u1 n2/u2 -- n3/u3 subtract n1-n2
< n1 n2 -- flag test n1<n2, signed
= x1 x2 -- flag test x1=x2
> n1 n2 -- flag test n1>n2, signed
>R x -- R: -- x push to return stack
?DUP x -- 0 | x x DUP if nonzero
@ a-addr -- x fetch cell from memory
0< n -- flag true if TOS negative
0= n/u -- flag return true if TOS=0
1+ n1/u1 -- n2/u2 add 1 to TOS
1- n1/u1 -- n2/u2 subtract 1 from TOS
2* x1 -- x2 arithmetic left shift
2/ x1 -- x2 arithmetic right shift
AND x1 x2 -- x3 logical AND
CONSTANT n -- define a Forth constant
C! c c-addr -- store char in memory
C@ c-addr -- c fetch char from memory
DROP x -- drop top of stack
DUP x -- x x duplicate top of stack
EMIT c -- output character to console
EXECUTE i*x xt -- j*x execute Forth word 'xt'
EXIT -- exit a colon definition
FILL c-addr u c -- fill memory with char
I -- n R: sys1 sys2 -- sys1 sys2
get the innermost loop index
INVERT x1 -- x2 bitwise inversion
J -- n R: 4*sys -- 4*sys
get the second loop index
KEY -- c get character from keyboard
LSHIFT x1 u -- x2 logical L shift u places
NEGATE x1 -- x2 two's complement
OR x1 x2 -- x3 logical OR
OVER x1 x2 -- x1 x2 x1 per stack diagram
ROT x1 x2 x3 -- x2 x3 x1 per stack diagram
RSHIFT x1 u -- x2 logical R shift u places
R> -- x R: x -- pop from return stack
R@ -- x R: x -- x fetch from rtn stk
SWAP x1 x2 -- x2 x1 swap top two items
UM* u1 u2 -- ud unsigned 16x16->32 mult.
UM/MOD ud u1 -- u2 u3 unsigned 32/16->16 div.
UNLOOP -- R: sys1 sys2 -- drop loop parms
U< u1 u2 -- flag test u1<n2, unsigned
VARIABLE -- define a Forth variable
XOR x1 x2 -- x3 logical XOR
ANS Forth Extensions
These are optional words whose definitions are
specified by the ANS Forth document.
<> x1 x2 -- flag test not equal
BYE i*x -- return to CP/M
CMOVE c-addr1 c-addr2 u -- move from bottom
CMOVE> c-addr1 c-addr2 u -- move from top
KEY? -- flag return true if char waiting
M+ d1 n -- d2 add single to double
NIP x1 x2 -- x2 per stack diagram
TUCK x1 x2 -- x2 x1 x2 per stack diagram
U> u1 u2 -- flag test u1>u2, unsigned
Private Extensions
These are words which are unique to CamelForth.
Many of these are necessary to implement ANS
Forth words, but are not specified by the ANS
document. Others are functions I find useful.
(do) n1|u1 n2|u2 -- R: -- sys1 sys2
run-time code for DO
(loop) R: sys1 sys2 -- | sys1 sys2
run-time code for LOOP
(+loop) n -- R: sys1 sys2 -- | sys1 sys2
run-time code for +LOOP
>< x1 -- x2 swap bytes
?branch x -- branch if TOS zero
BDOS DE C -- A call CP/M BDOS
branch -- branch always
lit -- x fetch inline literal to stack
PC! c p-addr -- output char to port
PC@ p-addr -- c input char from port
RP! a-addr -- set return stack pointer
RP@ -- a-addr get return stack pointer
SCAN c-addr1 u1 c -- c-addr2 u2
find matching char
SKIP c-addr1 u1 c -- c-addr2 u2
skip matching chars
SP! a-addr -- set data stack pointer
SP@ -- a-addr get data stack pointer
S= c-addr1 c-addr2 u -- n string compare
n<0: s1<s2, n=0: s1=s2, n>0: s1>s2
USER n -- define user variable 'n'
High level
TABLE 1. GLOSSARY OF "HIGH LEVEL" WORDS
(files CAMEL80D.AZM and CAMEL80H.AZM)
NAME stack in -- stack out description
Guide to stack diagrams: R: = return stack,
c = 8-bit character, flag = boolean (0 or -1),
n = signed 16-bit, u = unsigned 16-bit,
d = signed 32-bit, ud = unsigned 32-bit,
+n = unsigned 15-bit, x = any cell value,
i*x j*x = any number of cell values,
a-addr = aligned adrs, c-addr = character adrs
p-addr = I/O port adrs, sys = system-specific.
Refer to ANS Forth document for more details.
ANS Forth Core words
These are required words whose definitions are
specified by the ANS Forth document.
# ud1 -- ud2 convert 1 digit of output
#S ud1 -- ud2 convert remaining digits
#> ud1 -- c-addr u end conv., get string
' -- xt find word in dictionary
( -- skip input until )
* n1 n2 -- n3 signed multiply
*/ n1 n2 n3 -- n4 n1*n2/n3
*/MOD n1 n2 n3 -- n4 n5 n1*n2/n3, rem & quot
+LOOP adrs -- L: 0 a1 a2 .. aN --
, x -- append cell to dict
/ n1 n2 -- n3 signed divide
/MOD n1 n2 -- n3 n4 signed divide, rem & quot
: -- begin a colon definition
; end a colon definition
<# -- begin numeric conversion
>BODY xt -- a-addr adrs of param field
>IN -- a-addr holds offset into TIB
>NUMBER ud adr u -- ud' adr' u'
convert string to number
2DROP x1 x2 -- drop 2 cells
2DUP x1 x2 -- x1 x2 x1 x2 dup top 2 cells
2OVER x1 x2 x3 x4 -- x1 x2 x3 x4 x1 x2 per diag
2SWAP x1 x2 x3 x4 -- x3 x4 x1 x2 per diagram
2! x1 x2 a-addr -- store 2 cells
2@ a-addr -- x1 x2 fetch 2 cells
ABORT i*x -- R: j*x -- clear stack & QUIT
ABORT" i*x 0 -- i*x R: j*x -- j*x print msg &
i*x x1 -- R: j*x -- abort,x1<>0
ABS n1 -- +n2 absolute value
ACCEPT c-addr +n -- +n' get line from terminal
ALIGN -- align HERE
ALIGNED addr -- a-addr align given addr
ALLOT n -- allocate n bytes in dict
BASE -- a-addr holds conversion radix
BEGIN -- adrs target for backward branch
BL -- char an ASCII space
C, char -- append char to dict
CELLS n1 -- n2 cells->adrs units
CELL+ a-addr1 -- a-addr2 add cell size to adrs
CHAR -- char parse ASCII character
CHARS n1 -- n2 chars->adrs units
CHAR+ c-addr1 -- c-addr2 add char size to adrs
COUNT c-addr1 -- c-addr2 u counted->adr/len
CR -- output newline
CREATE -- create an empty definition
DECIMAL -- set number base to decimal
DEPTH -- +n number of items on stack
DO -- adrs L: -- 0 start of DO..LOOP
DOES> -- change action of latest def'n
ELSE adrs1 -- adrs2 branch for IF..ELSE
ENVIRONMENT? c-addr u -- false system query
EVALUATE i*x c-addr u -- j*x interpret string
FIND c-addr -- c-addr 0 ..if name not found
xt 1 ..if immediate
xt -1 ..if "normal"
FM/MOD d1 n1 -- n2 n3 floored signed division
HERE -- addr returns dictionary pointer
HOLD char -- add char to output string
IF -- adrs conditional forward branch
IMMEDIATE -- make last def'n immediate
LEAVE -- L: -- adrs exit DO..LOOP
LITERAL x -- append numeric literal to dict.
LOOP adrs -- L: 0 a1 a2 .. aN --
MAX n1 n2 -- n3 signed maximum
MIN n1 n2 -- n3 signed minimum
MOD n1 n2 -- n3 signed remainder
MOVE addr1 addr2 u -- smart move
M* n1 n2 -- d signed 16*16->32 multiply
POSTPONE -- postpone compile action of word
QUIT -- R: i*x -- interpret from keyboard
RECURSE -- recurse current definition
REPEAT adrs1 adrs2 -- resolve WHILE loop
SIGN n -- add minus sign if n<0
SM/REM d1 n1 -- n2 n3 symmetric signed division
SOURCE -- adr n current input buffer
SPACE -- output a space
SPACES n -- output n spaces
STATE -- a-addr holds compiler state
S" -- compile in-line string
." -- compile string to print
S>D n -- d single -> double precision
THEN adrs -- resolve forward branch
TYPE c-addr +n -- type line to terminal
UNTIL adrs -- conditional backward branch
U. u -- display u unsigned
. n -- display n signed
WHILE -- adrs branch for WHILE loop
WORD char -- c-addr n parse word delim by char
[ -- enter interpretive state
[CHAR] -- compile character literal
['] -- find word & compile as literal
] -- enter compiling state
ANS Forth Extensions
These are optional words whose definitions are
specified by the ANS Forth document.
.S -- print stack contents
/STRING a u n -- a+n u-n trim string
AGAIN adrs -- uncond'l backward branch
COMPILE, xt -- append execution token
DABS d1 -- +d2 absolute value, dbl.prec.
DNEGATE d1 -- d2 negate, double precision
HEX -- set number base to hex
PAD -- a-addr user PAD buffer
TIB -- a-addr Terminal Input Buffer
WITHIN n1|u1 n2|u2 n3|u3 -- f test n2<=n1<n3?
WORDS -- list all words in dict.
Private Extensions
These are words which are unique to CamelForth.
Many of these are necessary to implement ANS
Forth words, but are not specified by the ANS
document. Others are functions I find useful.
!CF adrs cfa -- set code action of a word
!COLON -- change code field to docolon
!DEST dest adrs -- change a branch dest'n
#INIT -- n #bytes of user area init data
'SOURCE -- a-addr two cells: len, adrs
(DOES>) -- run-time action of DOES>
(S") -- c-addr u run-time code for S"
,BRANCH xt -- append a branch instruction
,CF adrs -- append a code field
,DEST dest -- append a branch address
,EXIT -- append hi-level EXIT action
>COUNTED src n dst -- copy to counted str
>DIGIT n -- c convert to 0..9A..Z
>L x -- L: -- x move to Leave stack
?ABORT f c-addr u -- abort & print msg
?DNEGATE d1 n -- d2 negate d1 if n negative
?NEGATE n1 n2 -- n3 negate n1 if n2 negative
?NUMBER c-addr -- n -1 convert string->number
-- c-addr 0 if convert error
?SIGN adr n -- adr' n' f get optional sign
advance adr/n if sign; return NZ if negative
CELL -- n size of one cell
COLD -- cold start Forth system
COMPILE -- append inline execution token
DIGIT? c -- n -1 ..if c is a valid digit
-- x 0 ..otherwise
DP -- a-addr holds dictionary ptr
ENDLOOP adrs xt -- L: 0 a1 a2 .. aN --
HIDE -- "hide" latest definition
HP -- a-addr HOLD pointer
IMMED? nfa -- f fetch immediate flag
INTERPRET i*x c-addr u -- j*x
interpret given buffer
L0 -- a-addr bottom of Leave stack
LATEST -- a-addr last word in dictionary
LP -- a-addr Leave-stack pointer
L> -- x L: x -- move from Leave stack
NFA>CFA nfa -- cfa name adr -> code field
NFA>LFA nfa -- lfa name adr -> link field
R0 -- a-addr end of return stack
REVEAL -- "reveal" latest definition
S0 -- a-addr end of parameter stack
TIBSIZE -- n size of TIB
U0 -- a-addr current user area adrs
UD* ud1 d2 -- ud3 32*16->32 multiply
UD/MOD ud1 u2 -- u3 ud4 32/16->32 divide
UINIT -- addr initial values for user area
UMAX u1 u2 -- u unsigned maximum
UMIN u1 u2 -- u unsigned minimum