Apple-2-SW
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msbasic
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msbasic/flow.s

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.segment "CODE"
; ----------------------------------------------------------------------------
; "FOR" STATEMENT
;
; FOR PUSHES 18 BYTES ON THE STACK:
; 2 -- TXTPTR
; 2 -- LINE NUMBER
; 5 -- INITIAL (CURRENT) FOR VARIABLE VALUE
; 1 -- STEP SIGN
; 5 -- STEP VALUE
; 2 -- ADDRESS OF FOR VARIABLE IN VARTAB
; 1 -- FOR TOKEN ($81)
; ----------------------------------------------------------------------------
FOR:
lda #$80
sta SUBFLG
jsr LET
jsr GTFORPNT
bne L2619
txa
adc #FOR_STACK1
tax
txs
L2619:
pla
pla
lda #FOR_STACK2
jsr CHKMEM
jsr DATAN
clc
tya
adc TXTPTR
pha
lda TXTPTR+1
adc #$00
pha
lda CURLIN+1
pha
lda CURLIN
pha
lda #TOKEN_TO
jsr SYNCHR
jsr CHKNUM
jsr FRMNUM
lda FACSIGN
ora #$7F
and FAC+1
sta FAC+1
lda #<STEP
ldy #>STEP
sta INDEX
sty INDEX+1
jmp FRM_STACK3
; ----------------------------------------------------------------------------
; "STEP" PHRASE OF "FOR" STATEMENT
; ----------------------------------------------------------------------------
STEP:
lda #<CON_ONE
ldy #>CON_ONE
jsr LOAD_FAC_FROM_YA
jsr CHRGOT
cmp #TOKEN_STEP
bne L2665
jsr CHRGET
jsr FRMNUM
L2665:
jsr SIGN
jsr FRM_STACK2
lda FORPNT+1
pha
lda FORPNT
pha
lda #$81
pha
; ----------------------------------------------------------------------------
; PERFORM NEXT STATEMENT
; ----------------------------------------------------------------------------
NEWSTT:
jsr ISCNTC
lda TXTPTR
ldy TXTPTR+1
.ifdef CONFIG_2
cpy #>INPUTBUFFER
.endif
.ifdef CBM2
nop
.endif
.ifdef CONFIG_2
beq LC6D4
.else
beq L2683
.endif
sta OLDTEXT
sty OLDTEXT+1
LC6D4:
ldy #$00
L2683:
lda (TXTPTR),y
.ifndef CONFIG_11
beq LA5DC
cmp #$3A
beq NEWSTT2
SYNERR1:
jmp SYNERR
LA5DC:
.else
bne COLON
.endif
ldy #$02
lda (TXTPTR),y
clc
.ifdef CONFIG_2
jeq L2701
.else
beq L2701
.endif
iny
lda (TXTPTR),y
sta CURLIN
iny
lda (TXTPTR),y
sta CURLIN+1
tya
adc TXTPTR
sta TXTPTR
bcc NEWSTT2
inc TXTPTR+1
NEWSTT2:
jsr CHRGET
jsr EXECUTE_STATEMENT
jmp NEWSTT
; ----------------------------------------------------------------------------
; EXECUTE A STATEMENT
;
; (A) IS FIRST CHAR OF STATEMENT
; CARRY IS SET
; ----------------------------------------------------------------------------
EXECUTE_STATEMENT:
.ifndef CONFIG_11A
beq RET1
.ifndef APPLE
sec
.endif
.else
beq RET2
.endif
EXECUTE_STATEMENT1:
sbc #$80
.ifndef CONFIG_11
jcc LET
.else
bcc LET1
.endif
cmp #NUM_TOKENS
.ifdef CONFIG_2
bcs LC721
.else
bcs SYNERR1
.endif
asl a
tay
lda TOKEN_ADDRESS_TABLE+1,y
pha
lda TOKEN_ADDRESS_TABLE,y
pha
jmp CHRGET
.ifdef CONFIG_11
LET1:
jmp LET
COLON:
cmp #$3A
beq NEWSTT2
SYNERR1:
jmp SYNERR
.endif
.ifdef CONFIG_2
LC721:
.ifdef KBD
cmp #$45
.else
cmp #$4B
.endif
bne SYNERR1
jsr CHRGET
lda #TOKEN_TO
jsr SYNCHR
jmp GOTO
.endif
; ----------------------------------------------------------------------------
; "RESTORE" STATEMENT
; ----------------------------------------------------------------------------
RESTORE:
sec
lda TXTTAB
sbc #$01
ldy TXTTAB+1
bcs SETDA
dey
SETDA:
sta DATPTR
sty DATPTR+1
RET2:
rts
.ifndef CONFIG_CBM_ALL
; ----------------------------------------------------------------------------
; SEE IF CONTROL-C TYPED
; ----------------------------------------------------------------------------
ISCNTC:
.endif
.ifdef KBD
jsr LE8F3
bcc RET1
LE633:
jsr LDE7F
beq STOP
cmp #$03
bne LE633
.endif
.ifdef OSI
jmp MONISCNTC
nop
nop
nop
nop
lsr a
bcc RET2
jsr GETLN
cmp #$03
.endif
.ifdef APPLE
lda $C000
cmp #$83
beq L0ECC
rts
L0ECC:
jsr RDKEY
cmp #$03
.endif
.ifdef KIM
lda #$01
bit $1740
bmi RET2
ldx #$08
lda #$03
clc
cmp #$03
.endif
; ----------------------------------------------------------------------------
; "STOP" STATEMENT
; ----------------------------------------------------------------------------
STOP:
bcs END2
; ----------------------------------------------------------------------------
; "END" STATEMENT
; ----------------------------------------------------------------------------
END:
clc
END2:
bne RET1
lda TXTPTR
ldy TXTPTR+1
.ifdef CONFIG_2
ldx CURLIN+1
inx
.endif
beq END4
sta OLDTEXT
sty OLDTEXT+1
CONTROL_C_TYPED:
lda CURLIN
ldy CURLIN+1
sta OLDLIN
sty OLDLIN+1
END4:
pla
pla
L2701:
lda #<QT_BREAK
ldy #>QT_BREAK
.ifndef KBD
ldx #$00
stx Z14
.endif
bcc L270E
jmp PRINT_ERROR_LINNUM
L270E:
jmp RESTART
.ifdef KBD
LE664:
tay
jmp SNGFLT
.endif
; ----------------------------------------------------------------------------
; "CONT" COMMAND
; ----------------------------------------------------------------------------
CONT:
bne RET1
ldx #ERR_CANTCONT
ldy OLDTEXT+1
bne L271C
jmp ERROR
L271C:
lda OLDTEXT
sta TXTPTR
sty TXTPTR+1
lda OLDLIN
ldy OLDLIN+1
sta CURLIN
sty CURLIN+1
RET1:
rts
.ifdef KBD
PRT:
jsr GETBYT
txa
ror a
ror a
ror a
sta $8F
rts
LE68C:
ldy #$12
LE68E:
lda LEA30,y
sta $03A2,y
dey
bpl LE68E
rts
.endif
.if .def(CONFIG_NULL) || .def(CBM1)
; CBM1 has the keyword removed,
; but the code is still here
NULL:
jsr GETBYT
bne RET1
inx
cpx #NULL_MAX
bcs L2739
dex
stx Z15
rts
L2739:
jmp IQERR
.endif
.ifndef CONFIG_11A
CLEAR:
bne RET1
jmp CLEARC
.endif
.ifdef APPLE
.include "apple_loadsave.s"
.endif
.ifdef KIM
.include "kim_loadsave.s"
.endif
; ----------------------------------------------------------------------------
; "RUN" COMMAND
; ----------------------------------------------------------------------------
RUN:
bne L27CF
jmp SETPTRS
L27CF:
jsr CLEARC
jmp L27E9
; ----------------------------------------------------------------------------
; "GOSUB" STATEMENT
;
; LEAVES 7 BYTES ON STACK:
; 2 -- RETURN ADDRESS (NEWSTT)
; 2 -- TXTPTR
; 2 -- LINE #
; 1 -- GOSUB TOKEN
; ----------------------------------------------------------------------------
GOSUB:
lda #$03
jsr CHKMEM
lda TXTPTR+1
pha
lda TXTPTR
pha
lda CURLIN+1
pha
lda CURLIN
pha
lda #TOKEN_GOSUB
pha
L27E9:
jsr CHRGOT
jsr GOTO
jmp NEWSTT
; ----------------------------------------------------------------------------
; "GOTO" STATEMENT
; ALSO USED BY "RUN" AND "GOSUB"
; ----------------------------------------------------------------------------
GOTO:
jsr LINGET
jsr REMN
lda CURLIN+1
cmp LINNUM+1
bcs L2809
tya
sec
adc TXTPTR
ldx TXTPTR+1
bcc L280D
inx
bcs L280D
L2809:
lda TXTTAB
ldx TXTTAB+1
L280D:
.ifdef KBD
jsr LF457
bne UNDERR
.else
jsr FL1
bcc UNDERR
.endif
lda LOWTRX
sbc #$01
sta TXTPTR
lda LOWTRX+1
sbc #$00
sta TXTPTR+1
L281E:
rts
; ----------------------------------------------------------------------------
; "POP" AND "RETURN" STATEMENTS
; ----------------------------------------------------------------------------
POP:
bne L281E
lda #$FF
.ifdef CONFIG_2
sta FORPNT+1 ; bugfix, wrong in AppleSoft
.else
sta FORPNT
.endif
jsr GTFORPNT
txs
cmp #TOKEN_GOSUB
beq RETURN
ldx #ERR_NOGOSUB
.byte $2C
UNDERR:
ldx #ERR_UNDEFSTAT
jmp ERROR
; ----------------------------------------------------------------------------
SYNERR2:
jmp SYNERR
; ----------------------------------------------------------------------------
RETURN:
pla
pla
sta CURLIN
pla
sta CURLIN+1
pla
sta TXTPTR
pla
sta TXTPTR+1
; ----------------------------------------------------------------------------
; "DATA" STATEMENT
; EXECUTED BY SKIPPING TO NEXT COLON OR EOL
; ----------------------------------------------------------------------------
DATA:
jsr DATAN
; ----------------------------------------------------------------------------
; ADD (Y) TO TXTPTR
; ----------------------------------------------------------------------------
ADDON:
tya
clc
adc TXTPTR
sta TXTPTR
bcc L2852
inc TXTPTR+1
L2852:
rts
; ----------------------------------------------------------------------------
; SCAN AHEAD TO NEXT ":" OR EOL
; ----------------------------------------------------------------------------
DATAN:
ldx #$3A
.byte $2C
REMN:
ldx #$00
stx CHARAC
ldy #$00
sty ENDCHR
L285E:
lda ENDCHR
ldx CHARAC
sta CHARAC
stx ENDCHR
L2866:
lda (TXTPTR),y
beq L2852
cmp ENDCHR
beq L2852
iny
cmp #$22
.ifndef CONFIG_11
beq L285E
bne L2866
.else
bne L2866
beq L285E
.endif
; ----------------------------------------------------------------------------
; "IF" STATEMENT
; ----------------------------------------------------------------------------
IF:
jsr FRMEVL
jsr CHRGOT
cmp #TOKEN_GOTO
beq L2884
lda #TOKEN_THEN
jsr SYNCHR
L2884:
lda FAC
bne L288D
; ----------------------------------------------------------------------------
; "REM" STATEMENT, OR FALSE "IF" STATEMENT
; ----------------------------------------------------------------------------
REM:
jsr REMN
beq ADDON
L288D:
jsr CHRGOT
bcs L2895
jmp GOTO
L2895:
jmp EXECUTE_STATEMENT
; ----------------------------------------------------------------------------
; "ON" STATEMENT
;
; ON <EXP> GOTO <LIST>
; ON <EXP> GOSUB <LIST>
; ----------------------------------------------------------------------------
ON:
jsr GETBYT
pha
cmp #TOKEN_GOSUB
beq L28A4
L28A0:
cmp #TOKEN_GOTO
bne SYNERR2
L28A4:
dec FAC_LAST
bne L28AC
pla
jmp EXECUTE_STATEMENT1
L28AC:
jsr CHRGET
jsr LINGET
cmp #$2C
beq L28A4
pla
L28B7:
rts
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