everest% CC main3.C parse.C tree.C token.C bstring4.C main3.C: parse.C: tree.C: token.C: bstring4.C: everest% everest% a.out A calculator program. Enter blank line to quit. ? 3 + 4 = 7 ? 3 3 ParseError: Garbage at the end 3 3 ^--- syntax error ? 3 + 17 = 20 ? 17 - 2 * (1 + (4223 / 214) - 3) = -17 ? 7 * ( 6 + 5 * ( 4 + 3 * (2 + 1))) = 497 ? 7 * ( 6 + 5 * ( 4 + 3 * (2 + 1)) ParseError: Expecting ')' 7 * ( 6 + 5 * ( 4 + 3 * (2 + 1)) ^--- syntax error ? everest%