/**
* Constructs a lexer that will read from an input stream.
* @param in An input stream.
*/
explicit basic_lexer(const istream_type& in) :
basic_lexer(in.rdbuf())
{
// copy other input stream's state except for exception mask and
// unset failbit
this->_in.copyfmt(in);
this->_in.clear(in.rdstate() & ~std::ios_base::failbit);
}
my_istreambuf_iterator(istream_type& s) throw(): sbuf_(s.rdbuf()) { }
istreambuf_iterator(istream_type& s) noexcept :
istreambuf_iterator{s.rdbuf()} {}