PT[101]% bison -y -d ch3-02.y PT[102]% flex ch3-01.l PT[103]% gcc lex.yy.c y.tab.c -ll -ly PT[104]% ./a.out 3 + 4 * 5 = 23 PT[105]% ./a.out 3 + 4 * -5 = -17 PT[106]% ./a.out 3 - 4 + 5 = 4 PT[107]% ./a.out 3 - -4 + 5 = 12 PT[108]% ./a.out 5 / 2 = 2 PT[109]%