Hi everybody,
My Stack class here is used to performance a simply task of stack. I modified this class from another that has 2 parts, one is a structure making up the frame of the list's nodes , and the class is just responsible for building up the list. It's much clearer and easier to understand, but I try to combine them as one class as shown below.
Take a look at the destructor, each time one dynamic object created by push() function, right after that, it destroys that object once the push() function end. If I remove the destructor, this class work well, since pop() function is responsible for discarding the top node of the list. However, I want to implement the destructor for the class, is there the best way to deal with this ? Thanks in advance.
Here is my code :
Code:
#include <iostream>
#include "stack.h"
using namespace std;
//the class definition
class Stack
{
public:
Stack( );
//Initializes the object to an empty stack.
Stack(const Stack& a_stack);
//Copy constructor.
~Stack( );
//Destroys the stack and returns all the memory to the freestore.
void push(char the_symbol);
char pop( );
bool empty( ) const;
//Returns true if the stack is empty. Returns false otherwise.
private:
char data;
Stack *link;
Stack *top;
};
#endif //STACK_H
//Uses cstddef:
Stack::Stack( ) : data(NULL), link(NULL),top(NULL)
{
//empty.
}
Stack::Stack(const Stack& a_stack)
{
if (a_stack.top == NULL)
top = NULL;
else
{
Stack *temp = a_stack.top;//temp moves
//through the nodes from top to bottom of
//a_stack.
Stack *end;//Points to end of the new stack.
end = new Stack;
end->data = temp->data;
top = end;
//First node created and filled with data.
//New nodes are now added AFTER this first node.
temp = temp->link;
while (temp != NULL)
{
end->link = new Stack;
end = end->link;
end->data = temp->data;
temp = temp->link;
}
end->link = NULL;
}
}
Stack::~Stack( )
{
//destructor will be called when we push one node into the list
//so the node just borned will be destroyed immediately.
cout<<"check "<<pop()<<"-";
// I NEED HELP HERE ... ************************
}
//Uses cstddef:
bool Stack::empty( ) const
{
return (top == NULL);
}
//Uses cstddef:
void Stack::push(char the_symbol)
{
Stack *temp_ptr;
temp_ptr = new Stack;
temp_ptr->data = the_symbol;
temp_ptr->link = top;
top = temp_ptr;
//the destructor will be called when the dynamic variable pointed to by temp_ptr
//goes out of scope.
}
//Uses iostream:
char Stack::pop( )
{
if (empty( ))
{
cout << "Error: popping an empty stack.\n";
exit(1);
}
char result = top->data;
Stack *temp_ptr;
temp_ptr = top;
top = top->link;
delete temp_ptr;
return result;
}
// program body
int main( )
{
Stack s;
char next, ans;
do
{
cout << "Enter a word: ";
cin.get(next);
while (next != '\n')
{
s.push(next);
cin.get(next);
}
cout << "Written backward that is: ";
while ( ! s.empty( ) )
cout << s.pop( );
cout << endl;
cout << "Again?(y/n): ";
cin >> ans;
cin.ignore(10000, '\n');
}while (ans != 'n' && ans != 'N');
return 0;
}
