Handy LeftOf$() and RightOf$() Functions

[B+]

'Handy LeftOf and RightOf Functions.txt, by B+ 2018-09-09

calc$ = "1 - 2 + 3 - 4 + 5 - 6 + 7 - 8 + 9 - 10 + 11 - 12 + 13"
copyCalc$ = calc$

while len(calc$)
   nORo$ = LeftOf$(calc$, " ")
   calc$ = RightOf$(calc$, " ")
   if instr("+-", nORo$) then
       op$ = nORo$
   else
       select case op$
           case "" : sum = val(nORo$)
           case "+": sum = sum + val(nORo$)
           case "-": sum = sum - val(nORo$)
           case else : print "Error: maybe you forgot to include the LeftOf$() or RightOf$ functions?" : end
       end select
   end if
wend
print "And the sum of ";copyCalc$;" = ";sum

FUNCTION LeftOf$ (source$, of$)
   posOf = INSTR(source$, of$)
   IF posOf > 0 THEN LeftOf$ = MID$(source$, 1, posOf - 1)
END FUNCTION

FUNCTION RightOf$ (source$, of$)
   posOf = INSTR(source$, of$)
   IF posOf > 0 THEN RightOf$ = MID$(source$, posOf + LEN(of$))
END FUNCTION