%x COMMENT

%%
<INITIAL>"--"    {       BEGIN(COMMENT); }
<COMMENT>"\n"    { ECHO; BEGIN(INITIAL); }

<INITIAL>.       { ECHO; }
<COMMENT>.       {       }
%%

// https://westes.github.io/flex/manual/Start-Conditions.html

#include <stdlib.h>

int main(void) {
    
    yylex();

    return EXIT_SUCCESS;
}