RosettaCodeData/Task/Parsing-RPN-calculator-algo.../BBC-BASIC/parsing-rpn-calculator-algo...

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@% = &60B
RPN$ = "3 4 2 * 1 5 - 2 3 ^ ^ / +"
DIM Stack(1000)
SP% = 0
FOR i% = 1 TO LEN(RPN$)
Token$ = MID$(RPN$,i%,1)
IF Token$ <> " " THEN
PRINT Token$ " :";
CASE Token$ OF
WHEN "+": PROCpush(FNpop + FNpop)
WHEN "-": PROCpush(-FNpop + FNpop)
WHEN "*": PROCpush(FNpop * FNpop)
WHEN "/": n = FNpop : PROCpush(FNpop / n)
WHEN "^": n = FNpop : PROCpush(FNpop ^ n)
WHEN "0","1","2","3","4","5","6","7","8","9":
PROCpush(VALMID$(RPN$,i%))
WHILE ASCMID$(RPN$,i%)>=48 AND ASCMID$(RPN$,1)<=57
i% += 1
ENDWHILE
ENDCASE
FOR j% = SP%-1 TO 0 STEP -1 : PRINT Stack(j%); : NEXT
PRINT
ENDIF
NEXT i%
END
DEF PROCpush(n)
IF SP% > DIM(Stack(),1) ERROR 100, "Stack full"
Stack(SP%) = n
SP% += 1
ENDPROC
DEF FNpop
IF SP% = 0 ERROR 100, "Stack empty"
SP% -= 1
= Stack(SP%)