ladttex.cpp

经典c++程序的实现

const int LIST_SIZE = 10;

template <class ELEM>
class list {                // Array-based list class
private:
  int msize;                // Maximum size of list
  int numinlist;            // Actual number of ELEMs in list
  int curr;                 // Position of "current" ELEM
  ELEM* listarray;          // Array holding list ELEMs
public:
  list(const int =LIST_SIZE); // Constructor
  ~list();                  // Destructor
  void clear();             // Remove all ELEMs from list
  void insert(const ELEM&); // Insert ELEM at current position
  void append(const ELEM&); // Insert ELEM at tail of list
  ELEM remove();            // Remove and return current ELEM
  void setFirst();          // Set curr to first position
  void prev();              // Move curr to previous position
  void next();              // Move curr to next position
  int  length() const;      // Return current length of list
  void setPos(const int);   // Set curr to specified position
  void setValue(const ELEM&); // Set current ELEM's value
  ELEM currValue() const;   // Return current ELEM's value
  bool isEmpty() const;     // Return TRUE if list is empty
  bool isInList() const;    // TRUE if curr is within list
  bool find(const ELEM&);   // Find value (from current pos)
};

template <class ELEM>
list<ELEM>::list(const int sz) {  // Constructor: initialize
  msize = sz; numinlist = curr = 0;
  listarray = new ELEM[sz];
}
template <class ELEM>
list<ELEM>::~list()         // Destructor: return array space
  { delete [] listarray; }

template <class ELEM>
void list<ELEM>::clear()    // Remove all ELEMs from list
  { numinlist = curr = 0; } // Simply reinitialize values

// Insert ELEM at current position
template <class ELEM>
void list<ELEM>::insert(const ELEM& item) {
  // Array must not be full and curr must be a legal position
  assert((numinlist < msize) && (curr >=0)
                             && (curr <= numinlist));
  for(int i=numinlist; i>curr; i--) // Shift up to make room
    listarray[i] = listarray[i-1];
  listarray[curr] = item;
  numinlist++;              // Increment current list size
}

template <class ELEM>
void list<ELEM>::append(const ELEM& item) { // Insert at tail
  assert(numinlist < msize);  // List must not be full
  listarray[numinlist++] = item; // Increment list size
}

template <class ELEM>
ELEM list<ELEM>::remove() { // Remove and return current ELEM
  assert(!isEmpty() && isInList()); // Must be ELEM to remove
  ELEM temp = listarray[curr];        // Store removed ELEM
  for(int i=curr; i<numinlist-1; i++) // Shift elements down
    listarray[i] = listarray[i+1];
  numinlist--;              // Decrement current list size
  return temp;
}

template <class ELEM>
void list<ELEM>::setFirst()      // Set curr to first position
  { curr = 0; }

template <class ELEM>
void list<ELEM>::prev() { curr--; } // Move to previous pos

template <class ELEM>
void list<ELEM>::next() { curr++; } // Move to next position

template <class ELEM>
int list<ELEM>::length() const      // Return length of list
  { return    numinlist; }

template <class ELEM>
void list<ELEM>::setPos(const int pos) // Set to specified pos
  {curr = pos; }

int main() { // Create and use a list variable
   list<int> L1(15);
   list<double> L2;
   L1.append(12);
   L2.append(12.0);
}