%{
#include <stdio.h>
%}

letter [a-zA-Z]
digit [0-9]
letdigit {letter}|{digit}

%%

{letter}      { printf("Letter: %c\n", yytext[0]); }
{digit}       { printf("Digit: %c\n", yytext[0]); }
{letdigit}+   { printf("ID: %s\n", yytext); }
\n            { printf("New line character\n"); }
[ ]           { printf("space\n"); }
\'            { printf("single quote\n"); }
.             { /* ignore other characters */ }

%%

int main() {
    yylex();
    return 0;
}