%{ #define YY_SKIP_YYWRAP int yywrap(void) { return 1; } %} %option always-interactive %% [ \t]* { putchar('_'); } [0-9]+(\.[0-9]+)?(E[+\-]?[0-9]+)? { printf(""); ECHO; printf(""); } ([A-Z]|[a-z])([A-Z]|[a-z]|[0-9])* { printf(""); ECHO; printf(""); } "." { ECHO; exit(1); } . { ECHO; } \n { ECHO; fflush(stdout); } %% int main (void) { return yylex(); }