Reduceron

{
main = sum (take 10 (primes (enumFrom 2)));

take n [] = [];
take n (Cons x xs) = if (==) n 0 then [] else Cons x (take (n-1) xs);

sum l = sumAccum l 0;
sumAccum [] acc = acc;
sumAccum (Cons x xs) acc = sumAccum xs (x + acc);

sieve d l = mergeDiff l (myEnumFromThen d d) ;

primes (Cons x xs) = Cons x (sieve x (primes xs)) ;

mergeDiff xl yl =
  case xl of {
    Nil -> Nil ;
    Cons x xs ->
      case yl of {
        Nil -> Nil ;
        Cons y ys ->
          if (<=) x y then
            if (==) x y then
               mergeDiff xs ys
             else
               Cons x (mergeDiff xs yl)
          else
            mergeDiff xl ys;
        };
    };

enumFrom n = Cons n (enumFrom ((+) n 1));
myEnumFromThen x y = Cons x (myEnumFromThen ((+) x y) y);
};