Unextracting the previous character.
Declared in <bslstl_istringstream.h>
__istream_type&
unget();If rdbuf() is not null, calls rdbuf()->sungetc(c).
If rdbuf() is null or if sungetc() fails, sets badbit in the error state.
This function first clears eofbit. Since no characters are extracted, the next call to gcount() will return 0, as required by DR 60.
*this