tail cons X Y if true X if false Y primes sieve from s s 0 from X cons X head cons X X filter s s X cons Y if divides s s X Y sieve cons X cons X tail 1 cons 1 if 1 true 0 false 0 primes 0 sieve 1 from 1 s 1 0 0 head 1 filter 2 divides 2 FULL ./TRS/TRCSR/ExIntrod_GM99_L.trs