// 32-bit 2's-complement signed integer (int/Integer)
for (def i = 1; i > 0; i++) { println i }

// 64-bit 2's-complement signed integer (long/Long)
for (def i = 1L; i > 0; i+=1L) { println i }

// Arbitrarily-long binary signed integer (BigInteger)
for (def i = 1g; ; i+=1g) { println i }