using C++ Write a constant member function that returns a copy of the item at the rear of the queue.

Use the queue1.h and queue1.template files provided.

create a main() and Test the function in main()

// FILE: queue1.h (part of the namespace main_savitch_8B) // TEMPLATE CLASS PROVIDED: queue (a queue of items) // // TEMPLATE PARAMETER, TYPEDEFS and MEMBER CONSTANTS for the stack class: // The template parameter, Item, is the data type of the items in the queue, // also defined as queue::value_type. It may be any of the C++ built-in // types (int, char, etc.), or a class with a default constructor, a copy // constructor, and an assignment operator. The definition // queue::size_type is the data type of any variable that keeps track of // how many items are in a queue. The static const CAPACITY is the // maximum capacity of a queue for this first queue implementation. // NOTE: // Many compilers require the use of the new keyword typename before using // the expressions queue::value_type and queue::size_type. // Otherwise the compiler doesn't have enough information to realize that it // is the name of a data type. // // CONSTRUCTOR for the queue template class: // queue( ) // Postcondition: The queue has been initialized as an empty queue. // // MODIFICATION MEMBER FUNCTIONS for the queue template class: // void pop( ) // Precondition: size( ) > 0. // Postcondition: The front item of the queue has been removed. // // void push(const Item& entry) // Precondition: size( ) < CAPACITY. // Postcondition: A new copy of entry has been inserted at the rear of the // queue. // // CONSTANT MEMBER FUNCTIONS for the queue template class: // bool empty( ) const // Postcondition: The return value is true if the queue is empty. // // Item front( ) const // Precondition: size( ) > 0. // Postcondition: The return value is the front item of the queue (but the queue is // unchanged). // // size_type size( ) const // Postcondition: The return value is the total number of items in the queue. // // VALUE SEMANTICS for the queue template class: // Assignments and the copy constructor may be used with queue objects.

#ifndef MAIN_SAVITCH_QUEUE1_H #define MAIN_SAVITCH_QUEUE1_H #include // Provides size_t

namespace main_savitch_8B { template class queue { public: // TYPEDEFS and MEMBER CONSTANTS -- See Appendix E if this fails to compile. typedef std::size_t size_type; typedef Item value_type; static const size_type CAPACITY = 30; // CONSTRUCTOR queue( ); // MODIFICATION MEMBER FUNCTIONS void pop( ); void push(const Item& entry); // CONSTANT MEMBER FUNCTIONS bool empty( ) const { return (count == 0); } Item front( ) const; size_type size( ) const { return count; } private: Item data[CAPACITY]; // Circular array size_type first; // Index of item at front of the queue size_type last; // Index of item at rear of the queue size_type count; // Total number of items in the queue // HELPER MEMBER FUNCTION size_type next_index(size_type i) const { return (i+1) % CAPACITY; } }; }

#include "queue1.template" // Include the implementation. #endif

// FILE: queue1.template // TEMPLATE CLASS IMPLEMENTED: queue (see queue1.h for documentation) // This file is included in the header file, and not compiled separately. // INVARIANT for the queue class: // 1. The number of items in the queue is in the member variable count; // 2. For a non-empty queue, the items are stored in a circular array // beginning at data[front] and continuing through data[rear]. // The array's total capacity of the array is CAPACITY. // 3. For an empty array, rear is some valid index, and front is // always equal to next_index(rear). //

#include // Provides assert

namespace main_savitch_8B { template const typename queue::size_type queue::CAPACITY; template queue::queue( ) { count = 0; first = 0; last = CAPACITY - 1; }

template Item queue::front( ) const // Library facilities used: cassert { assert(!empty( )); return data[first]; }

template void queue::pop( ) // Library facilities used: cassert { assert(!empty( )); first = next_index(first); --count; } template void queue::push(const Item& entry) // Library facilities used: cassert { assert(size( ) < CAPACITY); last = next_index(last); data[last] = entry; ++count; }

}