forth: clarify the meaning of "wordref"
Also, make entry labels in dict.asm be wordref instead of entry ref.
This commit is contained in:
Virgil Dupras
parent
e8a4768304
commit
0e8af3cea4
@ -13,11 +13,8 @@
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nativeWord:
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jp (iy)
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; Execute a compiled word containing a list of references to other words,
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; usually ended by a reference to EXIT.
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; A reference to a word in a compiledWord section is *not* a direct reference,
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; but a word+CODELINK_OFFSET reference. Therefore, for a code link "link",
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; (link) is the routine to call.
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; Execute a list of atoms, which usually ends with EXIT.
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; IY points to that list.
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compiledWord:
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push iy \ pop hl
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inc hl
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@ -86,7 +83,7 @@ elseWord:
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inc bc \ inc bc
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call intoHL
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or a ; clear carry
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ld de, EXIT+CODELINK_OFFSET
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ld de, EXIT
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sbc hl, de
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jp z, exit
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; Not EXIT, let's continue with ELSE. No carry possible because EXIT
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@ -152,10 +149,10 @@ LIT:
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.dw litWord
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; ( R:I -- )
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EXIT:
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.db ";"
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.fill 7
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.dw 0
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EXIT:
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.dw nativeWord
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; When we call the EXIT word, we have to do a "double exit" because our current
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; Interpreter pointer is pointing to the word *next* to our EXIT reference when,
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@ -171,26 +168,26 @@ exit:
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jp compiledWord
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; ( R:I -- )
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QUIT:
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.db "QUIT", 0, 0, 0, 0
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.dw EXIT
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QUIT:
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.dw nativeWord
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quit:
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jp forthRdLine
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ABORT:
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.db "ABORT", 0, 0, 0
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.dw QUIT
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ABORT:
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.dw nativeWord
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abort:
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; Reinitialize PS (RS is reinitialized in forthInterpret
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ld sp, (INITIAL_SP)
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jp forthRdLine
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BYE:
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.db "BYE"
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.fill 5
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.dw ABORT
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BYE:
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.dw nativeWord
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; Goodbye Forth! Before we go, let's restore the stack
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ld sp, (INITIAL_SP)
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@ -201,9 +198,9 @@ BYE:
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ret
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; ( c -- )
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EMIT:
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.db "EMIT", 0, 0, 0, 0
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.dw BYE
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EMIT:
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.dw nativeWord
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pop hl
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ld a, l
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@ -211,13 +208,11 @@ EMIT:
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jp exit
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; ( addr -- )
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EXECUTE:
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.db "EXECUTE", 0
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.dw EMIT
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EXECUTE:
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.dw nativeWord
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pop iy ; Points to word_offset
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ld de, CODELINK_OFFSET
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add iy, de
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pop iy ; is a wordref
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executeCodeLink:
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ld l, (iy)
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ld h, (iy+1)
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@ -227,10 +222,10 @@ executeCodeLink:
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; IY points to PFA
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jp (hl) ; go!
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DEFINE:
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.db ":"
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.fill 7
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.dw EXECUTE
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DEFINE:
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.dw nativeWord
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call entryhead
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ld de, compiledWord
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@ -272,9 +267,9 @@ DEFINE:
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ld (HERE), de ; update HERE
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jp exit
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DOES:
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.db "DOES>", 0, 0, 0
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.dw DEFINE
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DOES:
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.dw nativeWord
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; We run this when we're in an entry creation context. Many things we
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; need to do.
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@ -285,8 +280,6 @@ DOES:
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; 3. exit. Because we've already popped RS, a regular exit will abort
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; colon definition, so we're good.
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ld iy, (CURRENT)
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ld de, CODELINK_OFFSET
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add iy, de
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ld hl, doesWord
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call wrCompHL
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inc iy \ inc iy ; cell variable space
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@ -296,10 +289,10 @@ DOES:
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jp exit
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; ( -- c )
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KEY:
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.db "KEY"
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.fill 5
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.dw DOES
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KEY:
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.dw nativeWord
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call stdioGetC
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ld h, 0
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@ -307,9 +300,9 @@ KEY:
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push hl
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jp exit
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INTERPRET:
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.db "INTERPRE"
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.dw KEY
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INTERPRET:
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.dw nativeWord
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interpret:
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ld iy, COMPBUF
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@ -319,14 +312,14 @@ interpret:
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call compile
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jr .loop
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.end:
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ld hl, QUIT+CODELINK_OFFSET
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ld hl, QUIT
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call wrCompHL
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ld iy, COMPBUF
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jp compiledWord
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CREATE:
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.db "CREATE", 0, 0
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.dw INTERPRET
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CREATE:
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.dw nativeWord
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call entryhead
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jp nz, quit
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@ -338,24 +331,24 @@ CREATE:
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ld (HERE), hl
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jp exit
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HERE_: ; Caution: conflicts with actual variable name
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.db "HERE"
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.fill 4
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.dw CREATE
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HERE_: ; Caution: conflicts with actual variable name
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.dw sysvarWord
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.dw HERE
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CURRENT_:
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.db "CURRENT", 0
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.dw HERE_
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CURRENT_:
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.dw sysvarWord
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.dw CURRENT
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; ( n -- )
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DOT:
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.db "."
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.fill 7
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.dw CURRENT_
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DOT:
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.dw nativeWord
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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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@ -367,10 +360,10 @@ DOT:
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jp exit
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; ( n a -- )
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STORE:
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.db "!"
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.fill 7
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.dw DOT
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STORE:
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.dw nativeWord
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pop iy
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pop hl
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@ -379,10 +372,10 @@ STORE:
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jp exit
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; ( a -- n )
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FETCH:
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.db "@"
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.fill 7
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.dw STORE
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FETCH:
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.dw nativeWord
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pop hl
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call intoHL
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@ -390,10 +383,10 @@ FETCH:
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jp exit
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; ( a b -- b a )
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SWAP:
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.db "SWAP"
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.fill 4
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.dw FETCH
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SWAP:
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.dw nativeWord
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pop hl
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ex (sp), hl
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@ -401,10 +394,10 @@ SWAP:
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jp exit
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; ( a -- a a )
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DUP:
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.db "DUP"
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.fill 5
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.dw SWAP
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DUP:
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.dw nativeWord
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pop hl
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push hl
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@ -412,10 +405,10 @@ DUP:
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jp exit
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; ( a b -- a b a )
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OVER:
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.db "OVER"
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.fill 4
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.dw DUP
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OVER:
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.dw nativeWord
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pop hl ; B
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pop de ; A
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@ -425,10 +418,10 @@ OVER:
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jp exit
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; ( a b -- c ) A + B
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PLUS:
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.db "+"
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.fill 7
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.dw OVER
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PLUS:
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.dw nativeWord
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pop hl
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pop de
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@ -437,10 +430,10 @@ PLUS:
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jp exit
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; ( a b -- c ) A - B
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MINUS:
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.db "-"
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.fill 7
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.dw PLUS
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MINUS:
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.dw nativeWord
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pop de ; B
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pop hl ; A
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@ -450,10 +443,10 @@ MINUS:
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jp exit
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; ( a b -- c ) A * B
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MULT:
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.db "*"
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.fill 7
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.dw MINUS
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MULT:
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.dw nativeWord
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pop de
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pop bc
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@ -462,10 +455,10 @@ MULT:
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jp exit
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; ( a b -- c ) A / B
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DIV:
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.db "/"
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.fill 7
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.dw MULT
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DIV:
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.dw nativeWord
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pop de
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pop hl
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@ -473,83 +466,83 @@ DIV:
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push bc
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jp exit
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IF:
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.db "IF"
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.fill 6
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.dw DIV
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IF:
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.dw ifWord
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ELSE:
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.db "ELSE"
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.fill 4
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.dw IF
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ELSE:
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.dw elseWord
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THEN:
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.db "THEN"
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.fill 4
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.dw ELSE
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THEN:
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.dw thenWord
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; End of native words
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; ( a -- )
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; @ .
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FETCHDOT:
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.db "?"
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.fill 7
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.dw THEN
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FETCHDOT:
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.dw compiledWord
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.dw FETCH+CODELINK_OFFSET
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.dw DOT+CODELINK_OFFSET
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.dw EXIT+CODELINK_OFFSET
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.dw FETCH
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.dw DOT
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.dw EXIT
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; ( n a -- )
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; SWAP OVER @ + SWAP !
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STOREINC:
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.db "+!"
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.fill 6
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.dw FETCHDOT
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STOREINC:
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.dw compiledWord
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.dw SWAP+CODELINK_OFFSET
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.dw OVER+CODELINK_OFFSET
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.dw FETCH+CODELINK_OFFSET
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.dw PLUS+CODELINK_OFFSET
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.dw SWAP+CODELINK_OFFSET
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.dw STORE+CODELINK_OFFSET
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.dw EXIT+CODELINK_OFFSET
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.dw SWAP
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.dw OVER
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.dw FETCH
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.dw PLUS
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.dw SWAP
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.dw STORE
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.dw EXIT
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; ( n -- )
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; HERE +!
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ALLOT:
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.db "ALLOT", 0, 0, 0
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.dw STOREINC
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ALLOT:
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.dw compiledWord
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.dw HERE_+CODELINK_OFFSET
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.dw STOREINC+CODELINK_OFFSET
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.dw EXIT+CODELINK_OFFSET
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.dw HERE_
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.dw STOREINC
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.dw EXIT
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; CREATE 2 ALLOT
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VARIABLE:
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.db "VARIABLE"
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.dw ALLOT
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VARIABLE:
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.dw compiledWord
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.dw CREATE+CODELINK_OFFSET
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.dw CREATE
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.dw NUMBER
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.dw 2
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.dw ALLOT+CODELINK_OFFSET
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.dw EXIT+CODELINK_OFFSET
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.dw ALLOT
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.dw EXIT
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; ( n -- )
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; CREATE HERE @ ! DOES> @
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CONSTANT:
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.db "CONSTANT"
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.dw VARIABLE
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CONSTANT:
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.dw compiledWord
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.dw CREATE+CODELINK_OFFSET
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.dw HERE_+CODELINK_OFFSET
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.dw FETCH+CODELINK_OFFSET
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.dw STORE+CODELINK_OFFSET
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.dw DOES+CODELINK_OFFSET
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.dw FETCH+CODELINK_OFFSET
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.dw EXIT+CODELINK_OFFSET
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.dw CREATE
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.dw HERE_
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.dw FETCH
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.dw STORE
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.dw DOES
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.dw FETCH
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.dw EXIT
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@ -1,19 +1,29 @@
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Stack notation: "<stack before> -- <stack after>". Rightmost is top of stack
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(TOS). For example, in "a b -- c d", b is TOS before, d is TOS
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after. "R:" means that the Return Stack is modified.
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(TOS). For example, in "a b -- c d", b is TOS before, d is TOS after. "R:" means
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that the Return Stack is modified.
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DOES>: Used inside a colon definition that itself uses CREATE, DOES> transforms
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that newly created word into a "does cell", that is, a regular cell (
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when called, puts the cell's addr on PS), but right after that, it
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executes words that appear after the DOES>.
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that newly created word into a "does cell", that is, a regular cell ( when
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called, puts the cell's addr on PS), but right after that, it executes words
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that appear after the DOES>.
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"does cells" always allocate 4 bytes (2 for the cell, 2 for the DOES>
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link) and there is no need for ALLOT in colon definition.
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"does cells" always allocate 4 bytes (2 for the cell, 2 for the DOES> link) and
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there is no need for ALLOT in colon definition.
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At compile time, colon definition stops processing words when reaching
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the DOES>.
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At compile time, colon definition stops processing words when reaching the
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DOES>.
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Example: ": CONSTANT CREATE HERE @ ! DOES> @ ;"
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Example: ": CONSTANT CREATE HERE @ ! DOES> @ ;"
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Word references (wordref): When we say we have a "word reference", it's a
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pointer to a words *code link*. For example, the label "PLUS:" in this unit is a
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word reference. Why not refer to the beginning of the word struct? Because we
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actually seldom refer to the name and prev link, except during compilation, so
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defining "word reference" this way makes the code easier to understand.
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Atom: A word of the type compiledWord contains, in its PF, a list of what we
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call "atoms". Those atoms are most of the time word references, but they can
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also be references to NUMBER and LIT.
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*** Native Words ***
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@ -27,11 +37,12 @@ DOES>: Used inside a colon definition that itself uses CREATE, DOES> transforms
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* a b -- c a * b -> c
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/ a b -- c a / b -> c
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CREATE x -- Create cell named x. Doesn't allocate a PF.
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CURRENT -- n Set n to wordref of last added entry.
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DOES> -- See description at top of file
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DUP a -- a a
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ELSE -- Branch to THEN
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EMIT c -- Spit char c to stdout
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EXECUTE a -- Execute word at addr a
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EXECUTE a -- Execute wordref at addr a
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HERE -- a Push HERE's address
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IF n -- Branch to ELSE or THEN if n is zero
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QUIT R:drop -- Return to interpreter promp immediately
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@ -6,7 +6,7 @@
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; Max length of dict entry names
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.equ NAMELEN 8
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; Offset of the code link relative to the beginning of the word
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.equ CODELINK_OFFSET 10
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.equ CODELINK_OFFSET NAMELEN+2
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; *** Variables ***
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.equ INITIAL_SP FORTH_RAMSTART
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@ -39,7 +39,7 @@ forthRdLine:
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ld (INPUTPOS), hl
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forthInterpret:
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ld ix, RS_ADDR-2 ; -2 because we inc-before-push
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ld iy, INTERPRET+CODELINK_OFFSET
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ld iy, INTERPRET
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jp executeCodeLink
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msgOk:
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.db " ok", 0
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@ -80,7 +80,7 @@ RSIsLIT:
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; Z if yes, NZ if no.
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RSIsEXIT:
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push de
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ld de, EXIT+CODELINK_OFFSET
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ld de, EXIT
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call RSIsDE
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pop de
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ret
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@ -163,14 +163,10 @@ readCompWord:
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.msg:
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.db "word expected", 0
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; For DE pointing to a dict entry, set DE to point to the previous entry.
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; For DE being a wordref, move DE to the previous wordref.
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; Z is set if DE point to 0 (no entry). NZ if not.
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prev:
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push hl ; --> lvl 1
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ld hl, NAMELEN ; prev field offset
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add hl, de
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ex de, hl
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pop hl ; <-- lvl 1
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dec de \ dec de ; prev field
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call intoDE
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; DE points to prev. Is it zero?
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xor a
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@ -183,15 +179,28 @@ prev:
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; point to that entry.
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; Z if found, NZ if not.
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find:
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push hl
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push bc
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ld de, (CURRENT)
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ld bc, CODELINK_OFFSET
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.inner:
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; DE is a wordref, let's go to beginning of struct
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push de ; --> lvl 1
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or a ; clear carry
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ex de, hl
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sbc hl, bc
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ex de, hl ; We're good, DE points to word name
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ld a, NAMELEN
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call strncmp
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ret z ; found
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pop de ; <-- lvl 1, return to wordref
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jr z, .end ; found
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call prev
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jr nz, .inner
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; Z set? end of dict unset Z
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inc a
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.end:
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pop bc
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pop hl
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ret
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; Write compiled data from HL into IY, advancing IY at the same time.
|
||||
@ -207,10 +216,7 @@ wrCompHL:
|
||||
compile:
|
||||
call find
|
||||
jr nz, .maybeNum
|
||||
; DE is a word offset, we need a code link
|
||||
ld hl, CODELINK_OFFSET
|
||||
add hl, de
|
||||
xor a ; set Z
|
||||
ex de, hl
|
||||
jr wrCompHL
|
||||
.maybeNum:
|
||||
push hl ; --> lvl 1. save string addr
|
||||
@ -250,13 +256,13 @@ entryhead:
|
||||
call strcpy
|
||||
ex de, hl ; (HERE) now in HL
|
||||
ld de, (CURRENT)
|
||||
ld (CURRENT), hl
|
||||
ld a, NAMELEN
|
||||
call addHL
|
||||
ld (hl), e
|
||||
inc hl
|
||||
ld (hl), d
|
||||
inc hl
|
||||
ld (CURRENT), hl
|
||||
ld (HERE), hl
|
||||
xor a ; set Z
|
||||
ret
|
||||
|
||||
Loading…
Reference in New Issue
Block a user