range function
Implementation
Iterable<int> range(int lenOrStart, [int? end]) {
int tmp;
if (end != null && end < lenOrStart) {
tmp = end;
end = lenOrStart;
lenOrStart = tmp;
}
return end == null
? Iterable.generate(lenOrStart, (index) => index)
: Iterable.generate(end - lenOrStart, (index) => lenOrStart++);
}