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forth: Forth-ify RECURSE
This comes with RS-modifying words. Also, this commit separates ";" from "EXIT", allowing EXIT to be used in definitions (was needed for RECURSE).
This commit is contained in:
Virgil Dupras
parent
c3838714d5
commit
d60ea4cb30
@ -14,3 +14,4 @@
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: = CMP NOT ;
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: < CMP 0 1 - = ;
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: > CMP 1 = ;
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: RECURSE R> R> 2 - >R >R EXIT ;
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@ -18,7 +18,7 @@
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; IP, but we also take care of increasing it my 2 before jumping
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next:
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; Before we continue: are stacks within bounds?
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call chkPS
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call chkPSRS
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ld de, (IP)
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ld h, d
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ld l, e
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@ -115,9 +115,10 @@ LIT:
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; Pop previous IP from Return stack and execute it.
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; ( R:I -- )
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.db ";"
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.fill 7
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.dw 0
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.db "EXIT"
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.fill 3
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.dw 0
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.db 0
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EXIT:
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.dw nativeWord
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call popRS
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@ -214,9 +215,18 @@ executeCodeLink:
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; IY points to PFA
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jp (hl) ; go!
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.db ";"
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.fill 6
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.dw EXECUTE
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.db 0
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ENDDEF:
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.dw nativeWord
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jp EXIT+2
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.db ":"
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.fill 6
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.dw EXECUTE
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.dw ENDDEF
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.db 0
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DEFINE:
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.dw nativeWord
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@ -232,7 +242,10 @@ DEFINE:
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ld (HERE), de ; update HERE
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ld hl, (IP)
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.loop:
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call HLPointsEXIT
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push de ; --> lvl 1
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ld de, ENDDEF
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call HLPointsDE
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pop de ; <-- lvl 1
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jr z, .loopend
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call compSkip
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jr .loop
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@ -358,9 +371,20 @@ KEY:
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push hl
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jp next
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.db "WORD"
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.fill 3
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.dw KEY
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.db 0
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WORD:
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.dw nativeWord
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call readword
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jp nz, abort
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push hl
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jp next
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.db "CREATE"
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.fill 1
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.dw KEY
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.dw WORD
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.db 0
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CREATE:
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.dw nativeWord
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@ -398,7 +422,7 @@ DOT:
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pop de
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; We check PS explicitly because it doesn't look nice to spew gibberish
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; before aborting the stack underflow.
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call chkPS
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call chkPSRS
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call pad
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call fmtDecimalS
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call printstr
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@ -454,7 +478,6 @@ CFETCH:
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push hl
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jp next
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; ( -- a )
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.db "LIT@"
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.fill 3
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.dw CFETCH
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@ -554,10 +577,63 @@ OVER2:
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push bc ; B
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jp next
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.db ">R"
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.fill 5
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.dw OVER2
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.db 0
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P2R:
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.dw nativeWord
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pop hl
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call pushRS
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jp next
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.db "R>"
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.fill 5
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.dw P2R
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.db 0
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R2P:
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.dw nativeWord
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call popRS
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push hl
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jp next
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.db "I"
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.fill 6
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.dw R2P
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.db 0
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I:
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.dw nativeWord
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ld l, (ix)
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ld h, (ix+1)
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push hl
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jp next
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.db "I'"
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.fill 5
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.dw I
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.db 0
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IPRIME:
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.dw nativeWord
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ld l, (ix-2)
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ld h, (ix-1)
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push hl
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jp next
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.db "J"
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.fill 6
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.dw IPRIME
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.db 0
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J:
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.dw nativeWord
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ld l, (ix-4)
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ld h, (ix-3)
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push hl
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jp next
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; ( a b -- c ) A + B
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.db "+"
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.fill 6
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.dw OVER2
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.dw J
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.db 0
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PLUS:
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.dw nativeWord
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@ -670,17 +746,6 @@ FBRC:
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ld (IP), hl
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jp next
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.db "RECURSE"
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.dw FBRC
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.db 0
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RECURSE:
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.dw nativeWord
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call popRS
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dec hl \ dec hl
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ld (IP), hl
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push hl \ pop iy
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jp compiledWord
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LATEST:
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.dw RECURSE
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.dw FBRC
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@ -60,7 +60,7 @@ QUIT R:drop -- Return to interpreter promp immediately
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RECURSE R:I -- R:I-2 Run the current word again.
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THEN I:a -- *I* Set branching cell at a.
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*** Stack ***
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*** Parameter Stack ***
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DUP a -- a a
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OVER a b -- a b a
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SWAP a b -- b a
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@ -68,6 +68,13 @@ SWAP a b -- b a
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2OVER a b c d -- a b c d a b
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2SWAP a b c d -- c d a b
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*** Return Stack ***
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>R n -- R:n Pops PS and push to RS
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R> R:n -- n Pops RS and push to PS
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I -- n Copy RS TOS to PS
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I' -- n Copy RS second item to PS
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J -- n Copy RS third item to PS
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*** Memory ***
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@ a -- n Set n to value at address a
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! n a -- Store n in address a
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@ -75,7 +82,7 @@ SWAP a b -- b a
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+! n a -- Increase value of addr a by n
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C@ a -- c Set c to byte at address a
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C! c a -- Store byte c in address a
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CURRENT -- n Set n to wordref of last added entry.
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CURRENT -- a Set a to wordref of last added entry.
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HERE -- a Push HERE's address
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H -- a HERE @
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@ -96,8 +103,8 @@ CMP n1 n2 -- n Compare n1 and n2 and set n to -1, 0, or 1.
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NOT f -- f Push the logical opposite of f
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*** Strings ***
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LIT@ x -- a Read folloing LIT and push its addr to a
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S= a1 a2 -- n Compare strings a1 and a2. See CMP
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LIT@ x -- a Read following LIT and push its addr to a
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SCMP a1 a2 -- n Compare strings a1 and a2. See CMP
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*** I/O ***
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. n -- Print n in its decimal form
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@ -105,4 +112,5 @@ EMIT c -- Spit char c to stdout
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KEY -- c Get char c from stdin
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PC! c a -- Spit c to port a
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PC@ a -- c Fetch c from port a
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WORD -- a Read one word from stdin and push its addr
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@ -17,8 +17,12 @@
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; *** Variables ***
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.equ INITIAL_SP FORTH_RAMSTART
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; wordref of the last entry of the dict.
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.equ CURRENT @+2
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; Pointer to the next free byte in dict. During compilation of input text, this
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; temporarily points to the next free byte in COMPBUF.
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.equ HERE @+2
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; Used to hold HERE while we temporarily point it to COMPBUF
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.equ OLDHERE @+2
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; Interpreter pointer. See Execution model comment below.
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.equ IP @+2
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@ -36,8 +36,15 @@ skipRS:
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pop hl
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ret
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; Verifies that SP is within bounds. If it's not, call ABORT
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chkPS:
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; Verifies that SP and RS are within bounds. If it's not, call ABORT
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chkPSRS:
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push ix \ pop hl
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push de ; --> lvl 1
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ld de, RS_ADDR
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or a ; clear carry
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sbc hl, de
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pop de ; <-- lvl 1
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jr c, .underflow
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ld hl, (INITIAL_SP)
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; We have the return address for this very call on the stack. Let's
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; compensate
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@ -45,6 +52,7 @@ chkPS:
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or a ; clear carry
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sbc hl, sp
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ret nc ; (INITIAL_SP) >= SP? good
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.underflow:
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; underflow
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ld hl, .msg
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call printstr
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@ -80,13 +80,6 @@ HLPointsBR:
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pop de
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ret
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HLPointsEXIT:
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push de
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ld de, EXIT
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call HLPointsDE
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pop de
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ret
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; Skip the compword where HL is currently pointing. If it's a regular word,
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; it's easy: we inc by 2. If it's a NUMBER, we inc by 4. If it's a LIT, we skip
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; to after null-termination.
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