Stacks Are Confusing

[student1115]

// project2.cpp : Defines the entry point for the console application.
//HELP ME I NEED TO DETERMINE BOUNDARY CONDITIONS IN THE
//STACK

//I ALSO NEED TO CHECK IF STACK IS EMPTY..SHOULD I MAKE //ANOTHER FUNCTION

//#include "stdafx.h"
#include "iostream.h"

class Stack {
private:

char *top;
char *bottom;



public:
Stack();
~Stack();
void push(char); // add a char to the stack
char pop(); // remove a char from the stack


};




Stack::Stack()
{
top = new char[20]; //dynamic memory allocation
bottom = top; //set bottom = top



}


Stack::~Stack()

{

delete top;

}


void Stack:ush( char c )
{

determine boudary conditions
if (*top > 1 && *top < 100)
{
++top;

*top = c;
}
}


char Stack:op()
{

// determine how to verify stack is not empty
//hint: check pointers..if pointers are equal.....

//if empty return character you defined

char ch;

ch = *top;
--top;

return(ch);
}






int main(int argc, char* argv[])
{
cout<<"Hello World!\n";

Stack *p_Stack;

p_Stack = new Stack;

p_Stack->push('a');
p_Stack->push('b');
p_Stack->push('c');
p_Stack->push('d');
cout << p_Stack->pop();

cout << endl;


return 0;
}

[ripper079]

//I ALSO NEED TO CHECK IF STACK IS EMPTY..SHOULD I MAKE //ANOTHER FUNCTION

I would implement a new data-member named size. This would keep track how many elements currently are in the stack. Create a function like isEmpty() to achive this (the user of your class shoudn´t have direct acces to size).

I don´t really understand your BOUNDARY CONDITIONS??? I would guess that you mean that a number that you push on the stack must be between x and y?!?!? If you explain it more i detail it would sertenly help.

I´ve also detected a memory leak in your prog.
In your destructor it should be

Stack::~Stack()
{
delete []top;
}

[Cela]

:-)

#include <iostream>

using namespace std;

namespace ansley {
  class stack {
    char *base;
    int   top;
    int   limit;
  public:
    explicit stack(int);
    ~stack();

    void push(char);
    char pop();

    bool empty() const;
    bool full() const;
  };

  stack::stack(int init_limit)
    : limit(init_limit), top(0)
  {
    base = new char[limit];
  }

  stack::~stack()
  {
    delete [] base;
  }

  void stack::push(char new_item)
  {
    if (!full())
    {
      base[top++] = new_item;
    }
    else
    {
      cerr<<"Stack is full"<<endl;
    }
  }

  char stack::pop()
  {
    if (!empty())
    {
      return base[--top];
    }
    else
    {
      cerr<<"Stack is empty"<<endl;
      return 0; // Return a safe value
    }
  }

  bool stack::empty() const
  {
    return top == 0;
  }

  bool stack::full() const
  {
    return top == limit;
  }
}

int main()
{
  ansley::stack mystack(3);

  mystack.push('a');
  mystack.push('b');
  mystack.push('c');
  mystack.push('d');

  cout<< mystack.pop() <<endl;
  cout<< mystack.pop() <<endl;
  cout<< mystack.pop() <<endl;
  cout<< mystack.pop() <<endl;
}

[student1115]

Thanks for your replay...I understand more clearly now..
but yes I do need boundary conditiions between 0 and 20 and i must use pointers...

I guess the instructor wants us to see the difference between using pointers in a stack from using arrays