moveBackTo abstract method
Moves the range to the last occurrence of target
before the current range.
If there is an occurrence of target
in the characters preceding
the current range,
then the new range contains exactly the last such occurrence of target
.
If there is no occurrence of target
after the current range,
the range is not modified.
Returns true
if the range is modified and false
if not.
Implementation
bool moveBackTo(Characters target);