Returns a String of length width padded with the same number of
characters on the left and right from fill. On the right, characters are
selected from fill starting at the end so that the last character in
fill is the last character in the result. fill is repeated if
neccessary to pad. [...]
Loops over s and returns traversed characters. Takes arbitrary from and
to indices. Works as a substitute for String.substring, except it never
throws RangeError. Supports negative indices. Think of an index as a
coordinate in an infinite in both directions vector filled with repeating
string s, whose 0-th coordinate coincides with the 0-th character in s.
Then loop returns the sub-vector defined by the interval (from, to).
from is inclusive. to is exclusive. [...]