-: / /MOD SWAP DROP ;
-: MOD /MOD DROP ;
+: \ IMMEDIATE
+ KEY
+ 10 = 0BRANCH [ -5 , ]
+; \ We can now comment!
-: '\n' 10 ;
-: BL 32 ;
+\ BASIC DEFINITIONS ----------------------------------------------------------------------
-: CR '\n' emit ;
-: SPACE BL emit ;
+: / /MOD SWAP DROP ;
+: MOD /MOD DROP ;
+: */ -ROT * SWAP / ;
-: NEGATE 0 swap - ;
+: NEGATE 0 SWAP - ;
: TRUE -1 ;
: FALSE 0 ;
: NOT 0= ;
-: LITERAL IMMEDIATE ' LIT , , ;
+\ Translate a number of cells into memory units
+\ (in our case 1 cell = 1 memory unit)
+: CELLS ;
+
+\ Since the smallest unit of memory in our system is 64 bits and since strings
+\ are stored as arrays of 64 bit integers, the character store/fetch words are
+\ just aliases of the standard store/fetch words.
+: C! ! ;
+: C@ @ ;
+: C, , ;
+
+: DEPTH PSP@ PSP0 @ - ;
+
+: '\n' 10 ;
+: BL 32 ;
+
+: LITERAL IMMEDIATE ['] LIT , , ;
-: ':'
- [
- CHAR :
- ]
- LITERAL
+: [CHAR] IMMEDIATE
+ CHAR
+ ['] LIT , ,
;
-: ';' [ CHAR ; ] LITERAL ;
-: '(' [ CHAR ( ] LITERAL ;
-: ')' [ CHAR ) ] LITERAL ;
-: '"' [ CHAR " ] LITERAL ;
-: 'A' [ CHAR A ] LITERAL ;
-: '0' [ CHAR 0 ] LITERAL ;
-: '-' [ CHAR - ] LITERAL ;
-: '.' [ CHAR . ] LITERAL ;
+: CR '\n' emit ;
+: SPACE BL emit ;
-\ While compiling, '[COMPILE] word' compiles 'word' if it would otherwise be IMMEDIATE.
: [COMPILE] IMMEDIATE
WORD \ get the next word
FIND \ find it in the dictionary
, \ and compile that
;
-\ RECURSE makes a recursive call to the current word that is being compiled.
-\
-\ Normally while a word is being compiled, it is marked HIDDEN so that references to the
-\ same word within are calls to the previous definition of the word. However we still have
-\ access to the word which we are currently compiling through the LATEST pointer so we
-\ can use that to compile a recursive call.
: RECURSE IMMEDIATE
LATEST @ \ LATEST points to the word being compiled at the moment
>CFA \ get the codeword
, \ compile it
;
-\ CONTROL STRUCTURES ----------------------------------------------------------------------
-\
-\ So far we have defined only very simple definitions. Before we can go further, we really need to
-\ make some control structures, like IF ... THEN and loops. Luckily we can define arbitrary control
-\ structures directly in FORTH.
-\
-\ Please note that the control structures as I have defined them here will only work inside compiled
-\ words. If you try to type in expressions using IF, etc. in immediate mode, then they won't work.
-\ Making these work in immediate mode is left as an exercise for the reader.
-
-\ condition IF true-part THEN rest
-\ -- compiles to: --> condition 0BRANCH OFFSET true-part rest
-\ where OFFSET is the offset of 'rest'
-\ condition IF true-part ELSE false-part THEN
-\ -- compiles to: --> condition 0BRANCH OFFSET true-part BRANCH OFFSET2 false-part rest
-\ where OFFSET if the offset of false-part and OFFSET2 is the offset of rest
-
-\ IF is an IMMEDIATE word which compiles 0BRANCH followed by a dummy offset, and places
-\ the address of the 0BRANCH on the stack. Later when we see THEN, we pop that address
-\ off the stack, calculate the offset, and back-fill the offset.
+: DEBUGON TRUE DEBUG ! ;
+: DEBUGOFF FALSE DEBUG ! ;
+
+\ CONTROL STRUCTURES ----------------------------------------------------------------------
+
: IF IMMEDIATE
- ' 0BRANCH , \ compile 0BRANCH
+ ['] 0BRANCH , \ compile 0BRANCH
HERE @ \ save location of the offset on the stack
0 , \ compile a dummy offset
;
;
: ELSE IMMEDIATE
- ' BRANCH , \ definite branch to just over the false-part
+ ['] BRANCH , \ definite branch to just over the false-part
HERE @ \ save location of the offset on the stack
0 , \ compile a dummy offset
SWAP \ now back-fill the original (IF) offset
SWAP !
;
-\ BEGIN loop-part condition UNTIL
-\ -- compiles to: --> loop-part condition 0BRANCH OFFSET
-\ where OFFSET points back to the loop-part
-\ This is like do { loop-part } while (condition) in the C language
: BEGIN IMMEDIATE
HERE @ \ save location on the stack
;
: UNTIL IMMEDIATE
- ' 0BRANCH , \ compile 0BRANCH
+ ['] 0BRANCH , \ compile 0BRANCH
HERE @ - \ calculate the offset from the address saved on the stack
, \ compile the offset here
;
-\ BEGIN loop-part AGAIN
-\ -- compiles to: --> loop-part BRANCH OFFSET
-\ where OFFSET points back to the loop-part
-\ In other words, an infinite loop which can only be returned from with EXIT
: AGAIN IMMEDIATE
- ' BRANCH , \ compile BRANCH
+ ['] BRANCH , \ compile BRANCH
HERE @ - \ calculate the offset back
, \ compile the offset here
;
-\ BEGIN condition WHILE loop-part REPEAT
-\ -- compiles to: --> condition 0BRANCH OFFSET2 loop-part BRANCH OFFSET
-\ where OFFSET points back to condition (the beginning) and OFFSET2 points to after the whole piece of code
-\ So this is like a while (condition) { loop-part } loop in the C language
: WHILE IMMEDIATE
- ' 0BRANCH , \ compile 0BRANCH
+ ['] 0BRANCH , \ compile 0BRANCH
HERE @ \ save location of the offset2 on the stack
0 , \ compile a dummy offset2
;
: REPEAT IMMEDIATE
- ' BRANCH , \ compile BRANCH
+ ['] BRANCH , \ compile BRANCH
SWAP \ get the original offset (from BEGIN)
HERE @ - , \ and compile it after BRANCH
DUP
SWAP ! \ and back-fill it in the original location
;
-\ UNLESS is the same as IF but the test is reversed.
-\
-\ Note the use of [COMPILE]: Since IF is IMMEDIATE we don't want it to be executed while UNLESS
-\ is compiling, but while UNLESS is running (which happens to be when whatever word using UNLESS is
-\ being compiled -- whew!). So we use [COMPILE] to reverse the effect of marking IF as immediate.
-\ This trick is generally used when we want to write our own control words without having to
-\ implement them all in terms of the primitives 0BRANCH and BRANCH, but instead reusing simpler
-\ control words like (in this instance) IF.
: UNLESS IMMEDIATE
- ' NOT , \ compile NOT (to reverse the test)
+ ['] NOT , \ compile NOT (to reverse the test)
[COMPILE] IF \ continue by calling the normal IF
;
-\ COMMENTS ----------------------------------------------------------------------
-\
-\ FORTH allows ( ... ) as comments within function definitions. This works by having an IMMEDIATE
-\ word called ( which just drops input characters until it hits the corresponding ).
+: DO IMMEDIATE
+ ['] LIT , -1 , [COMPILE] IF
+ ['] >R , ['] >R ,
+ ['] LIT , HERE @ 0 , ['] >R ,
+ HERE @
+;
+
+: ?DO IMMEDIATE
+ ['] 2DUP , ['] - , [COMPILE] IF
+ ['] >R , ['] >R ,
+ ['] LIT , HERE @ 0 , ['] >R ,
+ HERE @
+;
+
+: I RSP@ 3 - @ ;
+
+: J RSP@ 6 - @ ;
+
+: ?LEAVE IMMEDIATE
+ ['] 0BRANCH , 13 ,
+ ['] R> , ['] RDROP , ['] RDROP ,
+ ['] LIT , HERE @ 7 + , ['] DUP , ['] -ROT , ['] - , ['] SWAP , ['] ! ,
+ ['] BRANCH ,
+ 0 ,
+;
+
+: LEAVE IMMEDIATE
+ ['] LIT , -1 ,
+ [COMPILE] ?LEAVE
+;
+
+: +LOOP IMMEDIATE
+ ['] DUP , \ Store copy of increment
+
+ ['] R> , ['] SWAP , ['] R> , ['] SWAP , ['] R> , ['] SWAP , ['] + , ['] 2DUP , ['] - ,
+ ['] SWAP , ['] >R , ['] SWAP , ['] >R , ['] SWAP , ['] >R ,
+
+ \ Condition differently depending on sign of increment
+ ['] SWAP , ['] 0>= , [COMPILE] IF
+ ['] 0<= ,
+ [COMPILE] ELSE
+ ['] 0> ,
+ [COMPILE] THEN
+
+ \ Branch back to begining of loop kernel
+ ['] 0BRANCH , HERE @ - ,
+
+ \ Clean up
+ ['] RDROP , ['] RDROP , ['] RDROP ,
+
+ \ Record address of loop end for any LEAVEs to use
+ HERE @ SWAP !
+
+ [COMPILE] ELSE
+ ['] 2DROP , \ Clean up if loop was entirely skipped (?DO)
+ [COMPILE] THEN
+;
+
+: LOOP IMMEDIATE
+ ['] LIT , 1 ,
+ [COMPILE] +LOOP
+;
+
+
+\ CASE ------------------------------------------------------------------------
+
+: CASE IMMEDIATE
+ 0 \ push 0 to mark the bottom of the stack
+;
+
+: OF IMMEDIATE
+ ['] OVER , \ compile OVER
+ ['] = , \ compile =
+ [COMPILE] IF \ compile IF
+ ['] DROP , \ compile DROP
+;
+
+: ENDOF IMMEDIATE
+ [COMPILE] ELSE \ ENDOF is the same as ELSE
+;
+
+: ENDCASE IMMEDIATE
+ ['] DROP , \ compile DROP
+
+ \ keep compiling THEN until we get to our zero marker
+ BEGIN
+ ?DUP
+ WHILE
+ [COMPILE] THEN
+ REPEAT
+;
+
+
+\ COMMENTS ----------------------------------------------------------------------
+
: ( IMMEDIATE
1 \ allowed nested parens by keeping track of depth
BEGIN
KEY \ read next character
- DUP '(' = IF \ open paren?
+ DUP [CHAR] ( = IF \ open paren?
DROP \ drop the open paren
1+ \ depth increases
ELSE
- ')' = IF \ close paren?
+ [CHAR] ) = IF \ close paren?
1- \ depth decreases
THEN
THEN
DROP \ drop the depth counter
;
-(
- From now on we can use ( ... ) for comments.
-
- STACK NOTATION ----------------------------------------------------------------------
-
- In FORTH style we can also use ( ... -- ... ) to show the effects that a word has on the
- parameter stack. For example:
-
- ( n -- ) means that the word consumes an integer (n) from the parameter stack.
- ( b a -- c ) means that the word uses two integers (a and b, where a is at the top of stack)
- and returns a single integer (c).
- ( -- ) means the word has no effect on the stack
-)
-
( Some more complicated stack examples, showing the stack notation. )
: NIP ( x y -- y ) SWAP DROP ;
-: TUCK ( x y -- y x y ) DUP ROT ;
+: TUCK ( x y -- y x y ) DUP -ROT ;
: PICK ( x_u ... x_1 x_0 u -- x_u ... x_1 x_0 x_u )
1+ ( add one because of 'u' on the stack )
PSP@ SWAP - ( add to the stack pointer )
@ ( and fetch )
;
+: ROLL ( x_u x_u-1... x_0 u -- x_u-1 ... x_0 x_u )
+ 1+ DUP PICK SWAP ( x_u x_u-1 ... x_0 x_u u+1 )
+ PSP@ 1- SWAP - PSP@ 2- SWAP
+ DO
+ i 1+ @ i !
+ LOOP
+ SWAP DROP
+;
( With the looping constructs, we can now write SPACES, which writes n spaces to stdout. )
: SPACES ( n -- )
- BEGIN
- DUP 0> ( while n > 0 )
- WHILE
- SPACE ( print a space )
- 1- ( until we count down to 0 )
- REPEAT
- DROP
+ DUP 0> IF
+ 0 DO SPACE LOOP
+ ELSE
+ DROP
+ THEN
;
( Standard words for manipulating BASE. )
: DECIMAL ( -- ) 10 BASE ! ;
: HEX ( -- ) 16 BASE ! ;
-(
- PRINTING NUMBERS ----------------------------------------------------------------------
-
- The standard FORTH word . (DOT) is very important. It takes the number at the top
- of the stack and prints it out. However first I'm going to implement some lower-level
- FORTH words:
-
- U.R ( u width -- ) which prints an unsigned number, padded to a certain width
- U. ( u -- ) which prints an unsigned number
- .R ( n width -- ) which prints a signed number, padded to a certain width.
-
- For example:
- -123 6 .R
- will print out these characters:
- <space> <space> - 1 2 3
-
- In other words, the number padded left to a certain number of characters.
+( Compute absolute value. )
+: ABS ( n -- |n| )
+ dup 0< if
+ negate
+ then
+;
- The full number is printed even if it is wider than width, and this is what allows us to
- define the ordinary functions U. and . (we just set width to zero knowing that the full
- number will be printed anyway).
+: MAX ( n m -- max )
+ 2dup - 0< if
+ swap drop
+ else
+ drop
+ then
+;
- Another wrinkle of . and friends is that they obey the current base in the variable BASE.
- BASE can be anything in the range 2 to 36.
+: MIN ( n m -- max )
+ 2dup - 0> if
+ swap drop
+ else
+ drop
+ then
+;
- While we're defining . &c we can also define .S which is a useful debugging tool. This
- word prints the current stack (non-destructively) from top to bottom.
-)
+( PRINTING NUMBERS ---------------------------------------------------------------------- )
( This is the underlying recursive definition of U. )
: U. ( u -- )
( print the remainder )
DUP 10 < IF
- '0' ( decimal digits 0..9 )
+ [CHAR] 0 ( decimal digits 0..9 )
ELSE
10 - ( hex and beyond digits A..Z )
- 'A'
+ [CHAR] A
THEN
+
EMIT
;
+( This word returns the width (in characters) of an unsigned number in the current base )
+: UWIDTH ( u -- width )
+ BASE @ / ( rem quot )
+ ?DUP IF ( if quotient <> 0 then )
+ RECURSE 1+ ( return 1+recursive call )
+ ELSE
+ 1 ( return 1 )
+ THEN
+;
+
+: U.R ( u width -- )
+ SWAP ( width u )
+ DUP ( width u u )
+ UWIDTH ( width u uwidth )
+ ROT ( u uwidth width )
+ SWAP - ( u width-uwidth )
+ ( At this point if the requested width is narrower, we'll have a negative number on the stack.
+ Otherwise the number on the stack is the number of spaces to print. But SPACES won't print
+ a negative number of spaces anyway, so it's now safe to call SPACES ... )
+ SPACES
+ ( ... and then call the underlying implementation of U. )
+ U.
+;
+
+: .R ( n width -- )
+ SWAP ( width n )
+ DUP 0< IF
+ NEGATE ( width u )
+ 1 ( save a flag to remember that it was negative | width n 1 )
+ -ROT ( 1 width u )
+ SWAP ( 1 u width )
+ 1- ( 1 u width-1 )
+ ELSE
+ 0 ( width u 0 )
+ -ROT ( 0 width u )
+ SWAP ( 0 u width )
+ THEN
+ SWAP ( flag width u )
+ DUP ( flag width u u )
+ UWIDTH ( flag width u uwidth )
+ ROT ( flag u uwidth width )
+ SWAP - ( flag u width-uwidth )
+
+ SPACES ( flag u )
+ SWAP ( u flag )
+
+ IF ( was it negative? print the - character )
+ [CHAR] - EMIT
+ THEN
+
+ U.
+;
+
+: . 0 .R SPACE ;
+
+: .S ( -- )
+ [CHAR] < EMIT DEPTH U. [CHAR] > EMIT SPACE
+ PSP0 @ 1+
+ BEGIN
+ DUP PSP@ 2 - <=
+ WHILE
+ DUP @ .
+ 1+
+ REPEAT
+ DROP
+;
+
+: U. U. SPACE ;
+
+( ? fetches the integer at an address and prints it. )
+: ? ( addr -- ) @ . ;
+
+( c a b WITHIN returns true if a <= c and c < b )
+: WITHIN
+ -ROT ( b c a )
+ OVER ( b c a c )
+ <= IF
+ > IF ( b c -- )
+ TRUE
+ ELSE
+ FALSE
+ THEN
+ ELSE
+ 2DROP ( b c -- )
+ FALSE
+ THEN
+;
+
+
+( STRINGS ---------------------------------------------------------------------- )
+
+
+( Block copy, however, is important and novel: )
+: CMOVE ( src dest length -- )
+
+ DUP 0<= IF
+ EXIT
+ THEN
+
+ -ROT OVER - ( length src (dest-src) )
+ -ROT DUP ROT + SWAP ( (dest-src) (src+length) src )
+
+ DO
+ I @ ( (dest-src) i@ )
+ OVER I + ( (dest-src) i@ (dest-src+i) )
+ ! ( (dest-src) )
+ LOOP
+
+ DROP
+;
+
+( C, appends a byte to the current compiled word. )
+: C,
+ HERE @ C!
+ 1 HERE +!
+;
+
+: S" IMMEDIATE ( -- addr len )
+ STATE @ IF ( compiling? )
+ ['] LITSTRING , ( compile LITSTRING )
+ HERE @ ( save the address of the length word on the stack )
+ 0 , ( dummy length - we don't know what it is yet )
+ KEY DROP
+ BEGIN
+ KEY ( get next character of the string )
+ DUP [CHAR] " <>
+ WHILE
+ C, ( copy character )
+ REPEAT
+ DROP ( drop the double quote character at the end )
+ DUP ( get the saved address of the length word )
+ HERE @ SWAP - ( calculate the length )
+ 1- ( subtract 1 (because we measured from the start of the length word) )
+ SWAP ! ( and back-fill the length location )
+ ELSE ( immediate mode )
+ HERE @ ( get the start address of the temporary space )
+ KEY DROP
+ BEGIN
+ KEY
+ DUP [CHAR] " <>
+ WHILE
+ OVER C! ( save next character )
+ 1+ ( increment address )
+ REPEAT
+ DROP ( drop the final " character )
+ HERE @ - ( calculate the length )
+ HERE @ ( push the start address )
+ SWAP ( addr len )
+ THEN
+;
+
+: ." IMMEDIATE ( -- )
+ [COMPILE] S" ( read the string, and compile LITSTRING, etc. )
+ ['] TELL , ( compile the final TELL )
+;
+
+: .(
+ KEY DROP
+ BEGIN
+ KEY
+ DUP [CHAR] ) = IF
+ DROP ( drop the double quote character )
+ EXIT ( return from this function )
+ THEN
+ EMIT
+ AGAIN
+;
+
+
+( CONSTANTS AND VARIABLES ------------------------------------------------------ )
+
+: CONSTANT
+ WORD HEADER ( make dictionary entry (the name follows CONSTANT) )
+ DOCOL , ( append DOCOL (the codeword field of this word) )
+ ['] LIT , ( append the codeword LIT )
+ , ( append the value on the top of the stack )
+ ['] EXIT , ( append the codeword EXIT )
+;
+
+: ALLOT ( n -- )
+ HERE +! ( adds n to HERE, after this the old value of HERE is still on the stack )
+;
+
+: VARIABLE
+ CREATE
+ 1 CELLS ALLOT ( allocate 1 cell of memory, push the pointer to this memory )
+;
+
+
+: VALUE ( n -- )
+ WORD HEADER ( make the dictionary entry (the name follows VALUE) )
+ DOCOL , ( append DOCOL )
+ ['] LIT , ( append the codeword LIT )
+ , ( append the initial value )
+ ['] EXIT , ( append the codeword EXIT )
+;
+
+: TO IMMEDIATE ( n -- )
+ WORD ( get the name of the value )
+ FIND ( look it up in the dictionary )
+ >DFA ( get a pointer to the first data field (the 'LIT') )
+ 1+ ( increment to point at the value )
+ STATE @ IF ( compiling? )
+ ['] LIT , ( compile LIT )
+ , ( compile the address of the value )
+ ['] ! , ( compile ! )
+ ELSE ( immediate mode )
+ ! ( update it straightaway )
+ THEN
+;
+
+( x +TO VAL adds x to VAL )
+: +TO IMMEDIATE
+ WORD ( get the name of the value )
+ FIND ( look it up in the dictionary )
+ >DFA ( get a pointer to the first data field (the 'LIT') )
+ 1+ ( increment to point at the value )
+ STATE @ IF ( compiling? )
+ ['] LIT , ( compile LIT )
+ , ( compile the address of the value )
+ ['] +! , ( compile +! )
+ ELSE ( immediate mode )
+ +! ( update it straightaway )
+ THEN
+;
+
+( Fill u ints, starting at a, with the value b )
+: FILL ( a u b -- )
+ -ROT OVER + SWAP ?DO
+ DUP I !
+ LOOP
+ DROP
+;
+
+: ERASE ( a u -- )
+ 0 FILL
+;
+
+( PRINTING THE DICTIONARY ------------------------------------------------------ )
+
+: ID.
+ 1+ ( skip over the link pointer )
+ DUP @ ( get the flags/length byte )
+ F_LENMASK AND ( mask out the flags - just want the length )
+
+ BEGIN
+ DUP 0> ( length > 0? )
+ WHILE
+ SWAP 1+ ( addr len -- len addr+1 )
+ DUP @ ( len addr -- len addr char | get the next character)
+ DUP 32 >= OVER 127 <= AND IF
+ EMIT ( len addr char -- len addr | and print it)
+ ELSE
+ BASE @ SWAP HEX
+ ." \x" 0 .R
+ BASE !
+ THEN
+ SWAP 1- ( len addr -- addr len-1 | subtract one from length )
+ REPEAT
+ 2DROP ( len addr -- )
+;
+
+: ?HIDDEN
+ 1+ ( skip over the link pointer )
+ @ ( get the flags/length byte )
+ F_HIDDEN AND ( mask the F_HIDDEN flag and return it (as a truth value) )
+;
+: ?IMMEDIATE
+ 1+ ( skip over the link pointer )
+ @ ( get the flags/length byte )
+ F_IMMED AND ( mask the F_IMMED flag and return it (as a truth value) )
+;
+
+: WORDS
+ LATEST @ ( start at LATEST dictionary entry )
+ BEGIN
+ ?DUP ( while link pointer is not null )
+ WHILE
+ DUP ?HIDDEN NOT IF ( ignore hidden words )
+ DUP ID. ( but if not hidden, print the word )
+ SPACE
+ THEN
+ @ ( dereference the link pointer - go to previous word )
+ REPEAT
+ CR
+;
+
+
+( FORGET ---------------------------------------------------------------------- )
+
+: FORGET
+ WORD FIND ( find the word, gets the dictionary entry address )
+ DUP @ LATEST ! ( set LATEST to point to the previous word )
+ HERE ! ( and store HERE with the dictionary address )
+;
+
+( DUMP ------------------------------------------------------------------------ )
+
+\ TODO!
+
+
+( DECOMPILER ------------------------------------------------------------------ )
+
+: CFA>
+ LATEST @ ( start at LATEST dictionary entry )
+ BEGIN
+ ?DUP ( while link pointer is not null )
+ WHILE
+ 2DUP SWAP ( cfa curr curr cfa )
+ < IF ( current dictionary entry < cfa? )
+ NIP ( leave curr dictionary entry on the stack )
+ EXIT
+ THEN
+ @ ( follow link pointer back )
+ REPEAT
+ DROP ( restore stack )
+ 0 ( sorry, nothing found )
+;
+
+: SEE
+ WORD FIND ( find the dictionary entry to decompile )
+
+ ( Now we search again, looking for the next word in the dictionary. This gives us
+ the length of the word that we will be decompiling. (Well, mostly it does). )
+ HERE @ ( address of the end of the last compiled word )
+ LATEST @ ( word last curr )
+ BEGIN
+ 2 PICK ( word last curr word )
+ OVER ( word last curr word curr )
+ <> ( word last curr word<>curr? )
+ WHILE ( word last curr )
+ NIP ( word curr )
+ DUP @ ( word curr prev (which becomes: word last curr) )
+ REPEAT
+
+ DROP ( at this point, the stack is: start-of-word end-of-word )
+ SWAP ( end-of-word start-of-word )
+
+ DUP >CFA @ CASE
+ DOCOL OF
+ \ Colon definition
+ [CHAR] : EMIT SPACE DUP ID. SPACE
+ DUP ?IMMEDIATE IF ." IMMEDIATE " THEN CR
+ ENDOF
+ DOVAR OF
+ \ Variable definition
+ ." Variable " DUP ID. CR
+ 2DROP EXIT
+ ENDOF
+ DOCON OF
+ \ Constant definition
+ ." Constant " DUP ID. CR
+ 2DROP EXIT
+ ENDOF
+
+ \ Unknown codeword
+ ." Primitive or word with unrecognized codeword." CR
+ DROP 2DROP EXIT
+ ENDCASE
+
+ ( begin the definition with : NAME [IMMEDIATE] )
+ ( [CHAR] : EMIT SPACE DUP ID. SPACE
+ DUP ?IMMEDIATE IF ." IMMEDIATE " THEN CR 4 )
+
+ 4 SPACES
+
+ >DFA ( get the data address, ie. points after DOCOL | end-of-word start-of-data )
+
+ ( now we start decompiling until we hit the end of the word )
+ BEGIN ( end start )
+ 2DUP >
+ WHILE
+ DUP @ ( end start codeword )
+
+ CASE
+ ['] LIT OF ( is it LIT ? )
+ 1+ DUP @ ( get next word which is the integer constant )
+ . ( and print it )
+ ENDOF
+ ['] LITSTRING OF ( is it LITSTRING ? )
+ [CHAR] S EMIT [CHAR] " EMIT SPACE ( print S"<space> )
+ 1+ DUP @ ( get the length word )
+ SWAP 1+ SWAP ( end start+1 length )
+ 2DUP TELL ( print the string )
+ [CHAR] " EMIT SPACE ( finish the string with a final quote )
+ + ( end start+1+len, aligned )
+ 1- ( because we're about to add 4 below )
+ ENDOF
+ ['] 0BRANCH OF ( is it 0BRANCH ? )
+ ." 0BRANCH ( "
+ 1+ DUP @ ( print the offset )
+ .
+ ." ) "
+ ENDOF
+ ['] BRANCH OF ( is it BRANCH ? )
+ ." BRANCH ( "
+ 1+ DUP @ ( print the offset )
+ .
+ ." ) "
+ ENDOF
+ ['] ['] OF ( is it ['] ? )
+ ." ['] "
+ 1+ DUP @ ( get the next codeword )
+ CFA> ( and force it to be printed as a dictionary entry )
+ ID. SPACE
+ ENDOF
+ ['] EXIT OF ( is it EXIT? )
+ ( We expect the last word to be EXIT, and if it is then we don't print it
+ because EXIT is normally implied by ;. EXIT can also appear in the middle
+ of words, and then it needs to be printed. )
+ 2DUP ( end start end start )
+ 1+ ( end start end start+1 )
+ <> IF ( end start | we're not at the end )
+ ." EXIT "
+ THEN
+ ENDOF
+ ( default case: )
+ DUP ( in the default case we always need to DUP before using )
+ CFA> ( look up the codeword to get the dictionary entry )
+ ID. SPACE ( and print it )
+ ENDCASE
+
+ 1+ ( end start+1 )
+ REPEAT
+
+ [CHAR] ; EMIT CR
+
+ 2DROP ( restore stack )
+;
+
+
+( MEMORY ------------------------------------------------------------------ )
+: UNUSED ( -- cells )
+ MEMSIZE HERE @ - ;
The Lambda Lab / projects / forth.jl.git / blobdiff