/*?Code?for?exercise?10.12.
?|?
?|?“C++?Solutions--Companion?to?The?C++?Programming?Language?Third?Edition“
?|?by?David?Vandevoorde;?Addison-Wesley?1998;?ISBN?0-201-30965-3.
?|
?|?Permission?to?use?copy?modify?distribute?and?sell?this?software
?|?and?its?documentation?for?any?purpose?is?hereby?granted?without?fee.
?|?The?author?makes?no?representations?about?the?suitability?of?this
?|?software?for?any?purpose.??It?is?provided?“as?is“?without?express?or
?|?implied?warranty.
?‘----------------------------------------------------------------------*/

#include?
#include?

/*?The?following?can?go?in?a?header?file?*/

#include?
#include?

struct?Char_queue?{
???inline?Char_queue（unsigned?capacity?=?default_capacity）;
???~Char_queue（）?{?delete[]?queue_;?}
???bool?empty（）?const?{?return?head_==tail_;?}
???inline?char?dequeue（）;
???inline?void?enqueue（char）;
???bool?full（）?const?{?return?head_==（tail_+1）%capacity_;?}
???static?bool?const?fixed_capacity?=?true;
private:
???static?unsigned?const?default_capacity?=?32;
???char?*queue_;
???unsigned?head_?tail_;
???unsigned?const?capacity_;
};

inline
Char_queue::Char_queue（unsigned?n）
???:?queue_（new?char[n+1]）?head_（0）?tail_（0）?capacity_（n+1）?{
}

inline
char?Char_queue::dequeue（）?{
???if?（!empty（））?{
??????char?c?=?queue_[head_];
??????head_?=?（head_+1）%capacity_;
??????return?c;
???}?else
??????throw?std::underflow_error（std::string（“queue“））;
}

inline
void?Char_queue::enqueue（char?c）?{
???if?（!full（））?{
??????queue_[tail_]?=?c;
??????tail_?=?（tail_+1）%capacity_;
???}?else
??????throw?std::overflow_error（std::string（“queue“））;
}

/*?Header?file?would?stop?here.?*/

/*?A?brief?test?of?the?above?implementation:?*/

int?main（）?{
???Char_queue?q（4）;
???while?（1）?{
??????if?（q.empty（））?{?std::cout?<??????else?if?（q.full（））?{?std::cout?<??????char?cmd?ch;
??????std::cin?>>?cmd;
??????try?{
?????????switch?（cmd）?{
?????????case?‘e‘:?case?‘E‘:
????????????std::cin?>>?ch;
????????????q.enqueue（ch）;
????????????break;
?????????case?‘d‘:?case?‘D‘:
????????????std::cout?<????????????break;
?????????case?‘q‘:?case?‘Q‘:
????????????std::cout?<????????????return?0;
?????????default:
????????????std::cerr?<?????????}
??????}?catch?（std::exception?&x）?{
?????????std::cerr?<???????????????????<??????}
???}
???return?0;
}