# ncodeunits: Return the number of code units in a string (aking to index of vector). Not all such indices are valid – they may not be the start of a character,.
# sizeof: Size, in bytes, of the string str. Equal to the number of code units in str multiplied by the size, in bytes, of one code unit in str.
# lastindex: Return the last index of a collection
# nextinds(s, i): return the index of the start of the character whose encoding starts after index i
# nextind(s, 0, N): return the index of the Nth character of s (or, if there are less than N characters, return ncodeunits(str) + (N - length(s))