static L minus(Collection a, O... b) { Set set = asSet(b); new L l; for (O s : unnull(a)) if (!set.contains(s)) l.add(s); ret l; } static BigInteger minus(BigInteger a, BigInteger b) { ret a.subtract(b); } ifclass Complex static Complex minus(Complex c) { ret c == null ?: complex(-c.re(), -c.im()); } endif meta-for int also as double, long { static int minus(int a, int b) { ret a-b; } static int minus(int a) { ret -a; } }