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forth: add support for IMMEDIATE words

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This commit is contained in:
Virgil Dupras 2020-03-09 22:13:11 -04:00
parent 03bd9ee39b
commit 0b3f6253e4
3 changed files with 145 additions and 44 deletions
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112
apps/forth/dict.asm
View File

@ -243,34 +243,75 @@ DEFINE:
; been compiled by INTERPRET*. All those bytes will be copied as-is.
; All we need to do is to know how many bytes to copy. To do so, we
; skip compwords until EXIT is reached.
ld (HERE), hl ; where we write compwords.
ex de, hl ; DE is our dest
ld l, (ix)
ld h, (ix+1)
.loop:
call HLPointsEXIT
jr z, .loopend
call compSkip
call HLPointsNUMBER
jr nz, .notNUMBER
; is number
ld bc, 4
ldir
jr .loop
.loopend:
; At this point, HL points to EXIT compword. We'll copy it too.
; We'll use LDIR. BC will be RSTOP-OLDRSTOP+2
ld e, (ix)
ld d, (ix+1)
inc hl \ inc hl ; our +2
or a ; clear carry
sbc hl, de
ld b, h
ld c, l
; BC has proper count
ex de, hl ; HL is our source (old RS' TOS)
ld de, (HERE) ; and DE is our dest
ldir ; go!
.notNUMBER:
call HLPointsLIT
jr nz, .notLIT
; is lit
ldi
ldi
inc hl \ inc hl
call strcpyM
inc hl ; byte after word termination
jr .loop
.notLIT:
; it's a word
call HLPointsIMMED
jr nz, .notIMMED
; Immediate word, we'll have to call it.
; Before we make our call, let's save our current HL/DE position
ld (HERE), de
ld e, (hl)
inc hl
ld d, (hl)
inc hl ; point to next word
push de \ pop iy ; prepare for executeCodeLink
ld (ix), l
ld (ix+1), h
; Push return address
ld hl, .retList
call pushRS
; Ready!
jp executeCodeLink
.notIMMED:
; a good old regular word. We have 2 bytes to copy. But before we do,
; let's check whether it's an EXIT. LDI doesn't affect Z, so we can
; make our jump later.
call HLPointsEXIT
ldi
ldi
jr nz, .loop
; HL has our new RS' TOS
ld (ix), l
ld (ix+1), h
ld (HERE), de ; update HERE
jp exit
; This label is pushed to RS when an IMMED word is called. When that word calls
; exit, this is where it returns. When we return, RS will need to be popped so
; that we stay on the proper RS level.
.retList:
.dw .retWord
.retWord:
.dw .retEntry
.retEntry:
call popRS ; unwind stack
; recall old HL / DE values
ld l, (ix)
ld h, (ix+1)
ld de, (HERE)
; continue!
jr .loop
.db "DOES>"
.fill 3
.dw DEFINE
@ -293,10 +334,43 @@ DOES:
ld (HERE), iy
jp exit
.db "IMMEDIA"
.db 0
.dw DOES
IMMEDIATE:
.dw nativeWord
ld hl, (CURRENT)
dec hl
dec hl
dec hl
inc (hl)
jp exit
; ( n -- )
.db "LITERAL"
.db 1 ; IMMEDIATE
.dw IMMEDIATE
LITERAL:
.dw nativeWord
ld hl, (HERE)
ld de, NUMBER
ld (hl), e
inc hl
ld (hl), d
inc hl
pop de ; number from stack
ld (hl), e
inc hl
ld (hl), d
inc hl
ld (HERE), hl
jp exit
; ( -- c )
.db "KEY"
.fill 5
.dw DOES
.dw LITERAL
KEY:
.dw nativeWord
call stdioGetC

60
apps/forth/dictionary.txt
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@ -25,39 +25,49 @@ Atom: A word of the type compiledWord contains, in its PF, a list of what we
call "atoms". Those atoms are most of the time word references, but they can
also be references to NUMBER and LIT.
*** Native Words ***
*** Defining words ***
: x ... -- Define a new word
; R:I -- Exit a colon definition
. n -- Print n in its decimal form
ALLOT n -- Move HERE by n bytes
CREATE x -- Create cell named x. Doesn't allocate a PF.
CONSTANT x n -- Creates cell x that when called pushes its value
DOES> -- See description at top of file
IMMEDIATE -- Flag the latest defined word as immediate.
LITERAL n -- Inserts number from TOS as a literal
VARIABLE c -- Creates cell x with 2 bytes allocation.
*** Flow ***
ELSE -- Branch to THEN
EXECUTE a -- Execute wordref at addr a
IF n -- Branch to ELSE or THEN if n is zero
INTERPRET -- Get a line from stdin, compile it in tmp memory,
then execute the compiled contents.
QUIT R:drop -- Return to interpreter promp immediately
THEN -- Does nothing. Serves as a branching merker for IF
and ELSE.
*** Stack ***
DUP a -- a a
OVER a b -- a b a
SWAP a b -- b a
*** Memory ***
@ a -- n Set n to value at address a
! n a -- Store n in address a
? a -- Print value of addr a
+! n a -- Increase value of addr a by n
CURRENT -- n Set n to wordref of last added entry.
HERE -- a Push HERE's address
*** Arithmetic ***
+ a b -- c a + b -> c
- a b -- c a - b -> c
* a b -- c a * b -> c
/ a b -- c a / b -> c
CREATE x -- Create cell named x. Doesn't allocate a PF.
CURRENT -- n Set n to wordref of last added entry.
DOES> -- See description at top of file
DUP a -- a a
ELSE -- Branch to THEN
*** I/O ***
. n -- Print n in its decimal form
EMIT c -- Spit char c to stdout
EXECUTE a -- Execute wordref at addr a
HERE -- a Push HERE's address
IF n -- Branch to ELSE or THEN if n is zero
QUIT R:drop -- Return to interpreter promp immediately
KEY -- c Get char c from stdin
INTERPRET -- Get a line from stdin, compile it in tmp memory,
then execute the compiled contents.
OVER a b -- a b a
SWAP a b -- b a
THEN -- Does nothing. Serves as a branching merker for IF
and ELSE.
*** Core-but-Forth Words ***
? a -- Print value of addr a
+! n a -- Increase value of addr a by n
ALLOT n -- Move HERE by n bytes
CONSTANT x n -- Creates cell x that when called pushes its value
VARIABLE c -- Creates cell x with 2 bytes allocation.

17
apps/forth/util.asm
View File

@ -274,3 +274,20 @@ entryhead:
ld (HERE), hl
xor a ; set Z
ret
; Sets Z if wordref at (HL) is of the IMMEDIATE type
HLPointsIMMED:
push hl
call intoHL
dec hl
dec hl
dec hl
; We need an invert flag. We want to Z to be set when flag is non-zero.
ld a, 1
and (hl)
dec a ; if A was 1, Z is set. Otherwise, Z is unset
inc hl
inc hl
inc hl
pop hl
ret