///////    File OrderedSeq.h    ///////
typedef unsigned Uint;

class OrderedSeq  // abstract base class
{ public:
    OrderedSeq() : ordered(0) {}             // default constructor
    virtual int  enter(void* any);           // add any, -1 failed
    virtual void remove(Uint i)         =0;  // PURE remove by index
    virtual int  index(void* key);           // -1 if not found
    virtual Uint length()               =0;  // PURE current length of seq
    virtual ~OrderedSeq() {}                 // virtual destructor
  protected:
    virtual int  append(void* any)      =0;  // PURE add any at end, -1 failed
    virtual void sort();                     // sort into order
    virtual Uint sorted() { return ordered;} // 0 if arr is not sorted
    virtual void sorted(Uint s) 
    { ordered = s;}                          // set sorted flag
  private:
    virtual void swap(Uint i, Uint j)   =0;  // PURE interchange elements
    virtual int  cmp(Uint i, Uint j)    =0;  // PURE compare elements
    virtual int  cmp(void* key, Uint j) =0;  // PURE compare key to element
    void quicksort(int l, int r);
    Uint partition(int l, int r);
    Uint ordered;                            // sorted flag
};