books/cpp-bjarne/stack.cpp

   1 #include <iostream>
   2
   3 class Stack {
   4         private:
   5                 char *v;
   6                 int top;
   7                 int max_size;
   8         public:
   9                 class Underflow { }; // exception
  10                 class Overflow { };  // exception
  11                 class Bad_size { };  // exception
  12
  13                 Stack(int s);       // constructor
  14                 ~Stack();           // destructor
  15
  16                 void push(char c);
  17                 char pop();
  18 };
  19
  20 Stack::Stack(int s)
  21 {
  22         top = 0;
  23
  24         if (s > 1000)
  25                 throw Bad_size();
  26         max_size = s;
  27         v = new char[s]; // allocate elements on the free store (heap)
  28 }
  29
  30 Stack::~Stack()
  31 {
  32         delete[] v;
  33 }
  34
  35 void Stack::push(char c)
  36 {
  37         if (top == max_size)
  38                 throw Overflow();
  39         std::cout << v[top];
  40         v[top++] = c;
  41 }
  42
  43 char Stack::pop()
  44 {
  45         if (top == 0)
  46                 throw Underflow();
  47         return v[--top];
  48 }
  49
  50 Stack s_var1(10); // global stack with 10 elements
  51
  52 int main(void)
  53 {
  54         Stack s_var2(5); // local stack with 5 elements
  55         Stack *s_ptr = new Stack(20); // pointer to allocated stack
  56
  57         s_var1.push('f');
  58         s_var2.push('a');
  59         s_ptr->push('d');
  60
  61         std::cout << s_ptr->pop();
  62         std::cout << "\n";
  63
  64         try {
  65                 std::cout << s_ptr->pop();
  66         }
  67         catch (Stack::Underflow) {
  68                 std::cerr << "ERROR: No elements in the stack!\n";
  69                 return 1;
  70         }
  71
  72         return 0;
  73 }