02b.l

   1 %option noyywrap
   2 %option noinput
   3 %option nounput
   4 %{
   5 #include <stdio.h>
   6 int x = 0, z = 0, aim = 0;
   7 %}
   8
   9 %%
  10 forward\ [0-9] {
  11                 int num = atoi(yytext+sizeof("forward"));
  12                 x += num;
  13                 z += aim*num;
  14         }
  15 up\ [0-9]      aim -= atoi(yytext+sizeof("up"));
  16 down\ [0-9]    aim += atoi(yytext+sizeof("down"));
  17 \n      ;
  18 %%
  19
  20 int main (void)
  21 {
  22         yylex();
  23         printf("%d\n", x*z);
  24         return 0;
  25 }