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// FILE: bag5.template
// CLASS implemented: bag (see bag5.h for documentation)
// NOTE:
// Since bag is a template class, this file is included in node2.h.
// INVARIANT for the bag class:
// 1. The items in the bag are stored on a linked list;
// 2. The head pointer of the list is stored in the member variable head_ptr;
// 3. The total number of items in the list is stored in the member variable
// many_nodes.
#include <cassert> // Provides assert
#include <cstdlib> // Provides NULL, rand
#include "node2.h" // Provides node
namespace main_savitch_6B
{
template <class Item>
bag<Item>::bag( )
// Library facilities used: cstdlib
{
head_ptr = NULL;
many_nodes = 0;
}
template <class Item>
bag<Item>::bag(const bag<Item>& source)
// Library facilities used: node2.h
{
node<Item> *tail_ptr; // Needed for argument of list_copy
list_copy(source.head_ptr, head_ptr, tail_ptr);
many_nodes = source.many_nodes;
}
template <class Item>
bag<Item>::~bag( )
// Library facilities used: node2.h
{
list_clear(head_ptr);
many_nodes = 0;
}
template <class Item>
typename bag<Item>::size_type bag<Item>::count(const Item& target) const
// Library facilities used: cstdlib, node2.h
{
size_type answer;
const node<Item> *cursor;
answer = 0;
cursor = list_search(head_ptr, target);
while (cursor != NULL)
{
// Each time that cursor is not NULL, we have another occurrence of
// target, so we add one to answer, and move cursor to the next
// occurrence of the target.
++answer;
cursor = cursor->link( );
cursor = list_search(cursor, target);
}
return answer;
}
template <class Item>
typename bag<Item>::size_type bag<Item>::erase(const Item& target)
// Library facilities used: cstdlib, node2.h
{
size_type answer = 0;
node<Item> *target_ptr;
target_ptr = list_search(head_ptr, target);
while (target_ptr != NULL)
{
// Each time that target_ptr is not NULL, we have another occurrence
// of target. We remove this target using the same technique that
// was used in erase_one.
++answer;
target_ptr->set_data( head_ptr->data( ) );
target_ptr = target_ptr->link( );
target_ptr = list_search(target_ptr, target);
list_head_remove(head_ptr);
}
return answer;
}
template <class Item>
bool bag<Item>::erase_one(const Item& target)
// Library facilities used: cstdlib, node2.h
{
node<Item> *target_ptr;
target_ptr = list_search(head_ptr, target);
if (target_ptr == NULL)
return false; // target isn't in the bag, so no work to do
target_ptr->set_data( head_ptr->data( ) );
list_head_remove(head_ptr);
--many_nodes;
return true;
}
template <class Item>
Item bag<Item>::grab( ) const
// Library facilities used: cassert, cstdlib, node2.h
{
size_type i;
const node<Item> *cursor;
assert(size( ) > 0);
i = (std::rand( ) % size( )) + 1;
cursor = list_locate(head_ptr, i);
return cursor->data( );
}
template <class Item>
void bag<Item>::insert(const Item& entry)
// Library facilities used: node2.h
{
list_head_insert(head_ptr, entry);
++many_nodes;
}
template <class Item>
void bag<Item>::operator +=(const bag<Item>& addend)
// Library facilities used: node2.h
{
node<Item> *copy_head_ptr;
node<Item> *copy_tail_ptr;
if (addend.many_nodes > 0)
{
list_copy(addend.head_ptr, copy_head_ptr, copy_tail_ptr);
copy_tail_ptr->set_link( head_ptr );
head_ptr = copy_head_ptr;
many_nodes += addend.many_nodes;
}
}
template <class Item>
void bag<Item>::operator =(const bag<Item>& source)
// Library facilities used: node2.h
{
node<Item> *tail_ptr; // Needed for argument to list_copy
if (this == &source)
return;
list_clear(head_ptr);
many_nodes = 0;
list_copy(source.head_ptr, head_ptr, tail_ptr);
many_nodes = source.many_nodes;
}
template <class Item>
bag<Item> operator +(const bag<Item>& b1, const bag<Item>& b2)
{
bag<Item> answer;
answer += b1;
answer += b2;
return answer;
}
}
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