LocErrTest

10 REM > LocErrTest 0.10 15-Oct-2016 J.G.Harston

20 REM Source and demo code

30 :

40 REM Implement LOCAL ERROR and ON ERROR LOCAL for 6502 BASIC

50 REM Works within PROCs and FNs

60 :

70 :

80 PROCerr_local(1)

90 :

100 REM PROC test:

110 A%=-5

120 ON ERROR PRINT"Global PROC error: ";:REPORT:PRINT" at ";ERL:IF ERR=17:PROCerr_local(0):END

130 REPEAT

140 A%=A%+1:PROCtest(A%):IF A%=-3:ERROR 100,"Hello"

150 UNTIL A%=4:PRINT

160 :

170 REM FN test:

180 A%=-5

190 ON ERROR PRINT"Global FN error: ";:REPORT:PRINT" at ";ERL:IF ERR=17:PROCerr_local(0):END

200 REPEAT

210 A%=A%+1:B%=FNtest(A%):PRINT"Result=";B%:IF A%=-3:ERROR 100,"Hello"

220 UNTIL A%=4

230 :

240 PROCerr_local(0)

250 END

260 :

270 DEFPROCtest(A%)

280 LOCAL ERROR:ON ERROR LOCAL:PRINT"Local PROC error: ";:REPORT:PRINT" at ";ERL:ENDPROC

290 PRINT "100/";A%;"=";:PRINT ;100/A%

300 ENDPROC

310 :

320 DEFFNtest(A%)

330 LOCAL ERROR:ON ERROR LOCAL:PRINT"Local FN error: ";:REPORT:PRINT" at ";ERL:=FALSE

340 PRINT "100/";A%;"=";:PRINT ;100/A%

350 =TRUE

360 :

370 :

380 REM PROCerr_local(1) to enable local error handler

390 REM PROCerr_local(0) to restore default error handler

400 REM Usage: LOCAL ERROR:ON ERROR LOCAL local error handler

410 :

420 DEFPROCerr_local(A%):IF HIMEM>&FFFF:ENDPROC :REM Not 8-bit BASIC

430 IF (?&FFF7 AND &DF)<>&4C:ENDPROC :REM Not 6502 BASIC

440 IF A%=0:?&202=err_0%:?&203=err_0%DIV256:ENDPROC :REM Restore default handler

450 A%=!&202:REPEATA%=A%+1:UNTIL(!A%AND&8000FF)=&80004C :REM Find end of default handler

460 DIM err_% 119:FOR B%=0 TO 1:P%=err_%:[OPT 0

470 LDY #0:LDA (&FD),Y:CMP #16:BNE E% :\ Not Syntax error

480 LDY &0A:DEY:LDA (&0B),Y:CMP #&EA:BNE E%:.C% :\ Not LOCAL

490 INY:LDA (&0B),Y:CMP #32:BEQ C%:CMP #&85:BNE E% :\ Not LOCAL ERROR

500 INY:STY &0A:INC &1FB :\ Continue after 'ERROR'

510 LDA 4:SBC #8:STA 4:LDA 5:SBC #0:STA 5:LDY #7 :\ Make space on BASIC stack

520 LDA &1F9:STA (&04),Y:DEY:.D% :\ Stack overlapped byte from PTRB

530 LDA &12,Y:STA (&04),Y:DEY:CPY #3:BNE D% :\ Push !&16

540 LDA #0:STA (&04),Y:DEY:LDA #4:STA (&04),Y:DEY :\ Push 'word'

550 LDA #0:STA (&04),Y:DEY:LDA #&16:STA (&04),Y:BNE G%:\ Push &16

560 .E%

570 LDY #0:LDA (&16),Y:CMP #&EA:BEQ P%+5:.F%:JMP !&202:\ Not ON ERROR LOCAL

580 LDA &16:ADC #0:STA &0B:LDA &17:ADC #0:STA &0C :\ Continue after 'LOCAL'

590 LDA #0:STA &0A:.G%:LDX #&F5:TXS:JMP A%!1:]:NEXT :REM Restore stack and jump to execution loop

600 ?&202=err_%:?&203=err_%DIV256:err_0%=F%!1

610 ENDPROC

620 :