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3f3dd9141e | ||
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9c400ca642 | ||
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9d6cbe577c |
@ -9,15 +9,21 @@
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jp basStart
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; RAM space used in different routines for short term processing.
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.equ SCRATCHPAD_SIZE 0x20
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.equ SCRATCHPAD USER_RAMSTART
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.inc "core.asm"
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.inc "lib/util.asm"
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.inc "lib/ari.asm"
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.inc "lib/parse.asm"
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.inc "lib/fmt.asm"
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.equ EXPR_PARSE parseLiteral
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.equ EXPR_PARSE parseLiteralOrVar
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.inc "lib/expr.asm"
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.inc "basic/tok.asm"
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.equ BUF_RAMSTART USER_RAMSTART
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.equ VAR_RAMSTART SCRATCHPAD+SCRATCHPAD_SIZE
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.inc "basic/var.asm"
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.equ BUF_RAMSTART VAR_RAMEND
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.inc "basic/buf.asm"
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.equ BAS_RAMSTART BUF_RAMEND
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.inc "basic/main.asm"
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@ -1,28 +1,29 @@
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; *** Constants ***
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.equ BAS_SCRATCHPAD_SIZE 0x20
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; *** Variables ***
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; Value of `SP` when basic was first invoked. This is where SP is going back to
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; on restarts.
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.equ BAS_INITSP BAS_RAMSTART
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; **Pointer** to current line number
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.equ BAS_PCURLN @+2
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.equ BAS_SCRATCHPAD @+2
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.equ BAS_RAMEND @+BAS_SCRATCHPAD_SIZE
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; Pointer to next line to run. If nonzero, it means that the next line is
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; the first of the list. This is used by GOTO to indicate where to jump next.
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; Important note: this is **not** a line number, it's a pointer to a line index
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; in buffer. If it's not zero, its a valid pointer.
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.equ BAS_PNEXTLN @+2
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.equ BAS_RAMEND @+2
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; *** Code ***
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basStart:
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ld (BAS_INITSP), sp
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call varInit
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call bufInit
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xor a
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ld (BAS_PNEXTLN), a
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ld (BAS_PNEXTLN+1), a
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ld hl, .welcome
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call printstr
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call printcrlf
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ld hl, .welcome+2 ; points to a zero word
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ld (BAS_PCURLN), hl
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jr basLoop
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.welcome:
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.db "OK", 0, 0
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.db "OK", 0
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basLoop:
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ld hl, .sPrompt
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@ -39,8 +40,8 @@ basLoop:
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jr basLoop
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.number:
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push ix \ pop de
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call toWS
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call rdWS
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call toSep
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call rdSep
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call bufAdd
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jp nz, basERR
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jr basLoop
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@ -52,7 +53,10 @@ basLoop:
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; on success. Therefore, when calling basCallCmd results in NZ, we're not sure
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; where the error come from, but well...
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basCallCmd:
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; First, get cmd length
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; let's see if it's a variable assignment.
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call varTryAssign
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ret z ; Done!
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; Second, get cmd length
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call fnWSIdx
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cp 7
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jp nc, unsetZ ; Too long, can't possibly fit anything.
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@ -79,17 +83,13 @@ basCallCmd:
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ex de, hl
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ld a, b ; cmd's length
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call addHL
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call rdWS
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call rdSep
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jp (ix)
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basPrintLn:
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call printstr
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jp printcrlf
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basERR:
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ld hl, .sErr
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jr basPrintLn
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call printstr
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jp printcrlf
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.sErr:
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.db "ERR", 0
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@ -102,7 +102,8 @@ basERR:
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; Commands are expected to set Z on success.
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basBYE:
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ld hl, .sBye
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call basPrintLn
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call printstr
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call printcrlf
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; To quit the loop, let's return the stack to its initial value and
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; then return.
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xor a
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@ -117,7 +118,7 @@ basLIST:
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.loop:
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ld e, (ix)
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ld d, (ix+1)
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ld hl, BAS_SCRATCHPAD
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ld hl, SCRATCHPAD
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call fmtDecimal
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call printstr
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ld a, ' '
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@ -132,6 +133,8 @@ basLIST:
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basRUN:
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call .maybeGOTO
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jr nz, .loop ; IX already set
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call bufFirst
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ret nz
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.loop:
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@ -141,6 +144,8 @@ basRUN:
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call basCallCmd
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pop ix ; <-- lvl 1
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jp nz, .err
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call .maybeGOTO
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jr nz, .loop ; IX already set
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call bufNext
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jr z, .loop
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cp a ; ensure Z
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@ -149,23 +154,69 @@ basRUN:
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; Print line number, then return NZ (which will print ERR)
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ld e, (ix)
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ld d, (ix+1)
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ld hl, BAS_SCRATCHPAD
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ld hl, SCRATCHPAD
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call fmtDecimal
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call printstr
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ld a, ' '
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call stdioPutC
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jp unsetZ
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.runline:
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; This returns the opposite Z result as the one we usually see: Z is set if
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; we **don't** goto, unset if we do. If we do, IX is properly set.
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.maybeGOTO:
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ld de, (BAS_PNEXTLN)
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ld a, d
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or e
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ret z
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; we goto
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push de \ pop ix
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; we need to reset our goto marker
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ld de, 0
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ld (BAS_PNEXTLN), de
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ret
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basPRINT:
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ld de, SCRATCHPAD
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call rdWord
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push hl ; --> lvl 1
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ex de, hl
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call parseExpr
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ret nz
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push ix \ pop de
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ld hl, BAS_SCRATCHPAD
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ld hl, SCRATCHPAD
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call fmtDecimal
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call printstr
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pop hl ; <-- lvl 1
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; Do we have another arg?
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call rdSep
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jr z, .another
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; no, we can stop here
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cp a ; ensure Z
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jp basPrintLn
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jp printcrlf
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.another:
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; Before we jump to basPRINT, let's print a space
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ld a, ' '
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call stdioPutC
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jr basPRINT
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basGOTO:
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ld de, SCRATCHPAD
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call rdWord
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ex de, hl
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call parseExpr
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ret nz
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push ix \ pop de
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call bufFind
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jr nz, .notFound
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push ix \ pop de
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; Z already set
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jr .end
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.notFound:
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ld de, 0
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; Z already unset
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.end:
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ld (BAS_PNEXTLN), de
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ret
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; direct only
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basCmds1:
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@ -179,4 +230,6 @@ basCmds1:
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basCmds2:
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.dw basPRINT
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.db "print", 0
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.dw basGOTO
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.db "goto", 0, 0
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.db 0xff, 0xff, 0xff ; end of table
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@ -1,3 +1,12 @@
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; Sets Z is A is ' ' or '\t' (whitespace), or ',' (arg sep)
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isSep:
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cp ' '
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ret z
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cp 0x09
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ret z
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cp ','
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ret
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; Expect at least one whitespace (0x20, 0x09) at (HL), and then advance HL
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; until a non-whitespace character is met.
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; HL is advanced to the first non-whitespace char.
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@ -5,7 +14,7 @@
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; Failure is either not having a first whitespace or reaching the end of the
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; string.
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; Sets Z if we found a non-whitespace char, unset if we found the end of string.
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rdWS:
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rdSep:
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ld a, (hl)
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call isSep
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ret nz ; failure
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@ -47,10 +56,32 @@ fnWSIdx:
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pop hl
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ret
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; Advance HL to the next whitespace or to the end of string.
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toWS:
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; Advance HL to the next separator or to the end of string.
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toSep:
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ld a, (hl)
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call isSep
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ret z
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inc hl
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jr toWS
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jr toSep
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; Read (HL) until the next separator and copy it in (DE)
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; DE is preserved, but HL is advanced to the end of the read word.
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rdWord:
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push af
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push de
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.loop:
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ld a, (hl)
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call isSep
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jr z, .stop
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or a
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jr z, .stop
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ld (de), a
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inc hl
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inc de
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jr .loop
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.stop:
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xor a
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ld (de), a
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pop de
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pop af
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ret
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101
apps/basic/var.asm
Normal file
101
apps/basic/var.asm
Normal file
@ -0,0 +1,101 @@
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; *** Variables ***
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; A list of words for each member of the A-Z range.
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.equ VAR_TBL VAR_RAMSTART
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.equ VAR_RAMEND @+52
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; *** Code ***
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varInit:
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ld b, VAR_RAMEND-VAR_RAMSTART
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ld hl, VAR_RAMSTART
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xor a
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.loop:
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ld (hl), a
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inc hl
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djnz .loop
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ret
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; Check if A is a valid variable letter (a-z or A-Z). If it is, set A to a
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; valid VAR_TBL index and set Z. Otherwise, unset Z (and A is destroyed)
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varChk:
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call upcase
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sub 'A'
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ret c ; Z unset
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cp 27 ; 'Z' + 1
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jr c, .isVar
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; A > 'Z'
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dec a ; unset Z
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ret
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.isVar:
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cp a ; set Z
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ret
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; Try to interpret line at (HL) and see if it's a variable assignment. If it
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; is, proceed with the assignment and set Z. Otherwise, NZ.
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varTryAssign:
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inc hl
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ld a, (hl)
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dec hl
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cp '='
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ret nz
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ld a, (hl)
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call varChk
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ret nz
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; We have a variable! Its table index is currently in A.
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push ix ; --> lvl 1
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push hl ; --> lvl 2
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push de ; --> lvl 3
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push af ; --> lvl 4. save for later
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; Let's put that expression to read in scratchpad
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inc hl \ inc hl
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ld de, SCRATCHPAD
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call rdWord
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ex de, hl
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; Now, evaluate that expression now in (HL)
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call parseExpr ; --> number in IX
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jr nz, .exprErr
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pop af ; <-- lvl 4
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add a, a ; * 2 because each element is a word
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ld hl, VAR_TBL
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call addHL
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; HL placed, write number
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push ix \ pop de
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ld (hl), e
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inc hl
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ld (hl), d
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xor a ; ensure Z
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.end:
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pop de ; <-- lvl 3
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pop hl ; <-- lvl 2
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pop ix ; <-- lvl 1
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ret
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.exprErr:
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pop af ; <-- lvl 4
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jr .end
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; Check if value at (HL) is a variable. If yes, returns its associated value.
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; Otherwise, jump to parseLiteral.
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parseLiteralOrVar:
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inc hl
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ld a, (hl)
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dec hl
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or a
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; if more than one in length, it can't be a variable
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jp nz, parseLiteral
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ld a, (hl)
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call varChk
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jp nz, parseLiteral
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; It's a variable, resolve!
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add a, a ; * 2 because each element is a word
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push hl ; --> lvl 1
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ld hl, VAR_TBL
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call addHL
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push de ; --> lvl 2
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ld e, (hl)
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inc hl
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ld d, (hl)
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push de \ pop ix
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pop de ; <-- lvl 2
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pop hl ; <-- lvl 1
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cp a ; ensure Z
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ret
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@ -132,7 +132,7 @@ parseDecimal:
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pop hl
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ret z
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; A is not 0? Ok, but if it's a space, we're happy too.
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jp isSep
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jp isWS
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.error:
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pop hl
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jp unsetZ
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@ -1,5 +1,5 @@
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; Sets Z is A is ' ' or '\t'
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isSep:
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; Sets Z is A is ' ' or '\t' (whitespace)
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isWS:
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cp ' '
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ret z
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cp 0x09
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@ -31,7 +31,7 @@ isLineEnd:
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; Sets Z is A is ' ', ',', ';', CR, LF, or null.
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isSepOrLineEnd:
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call isSep
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call isWS
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ret z
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jr isLineEndOrComment
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@ -68,7 +68,7 @@ isLabel:
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; read char in A
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_eatWhitespace:
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call ioGetB
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call isSep
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call isWS
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ret nz
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jr _eatWhitespace
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