#ifndef STOPOS_KEY_H
#define STOPOS_KEY_H
#include <string>
#include <iostream>

class stopos_key
{
  protected:
    std::string value;
    static const char firstchar = 'a';
    static const char lastchar  = 'z';
    static const unsigned int base = lastchar - firstchar + 1;
    template <typename T> void tostring1(std::string &v,const T n)
    {
      if (n == 0)
        return;
      unsigned int c = n + firstchar - base*(n/base);
      tostring1(v,n/base);
      v.push_back(c);
    }
    template <typename T> void tostring(std::string &v,const T n)
    {
      if (n == 0)
	v = firstchar;
      else
	tostring1(v,n);
    }
  public:
    stopos_key();
    stopos_key(const std::string &s);
    void increment(void);
    std::string str(void) const;
    void impossible();
    bool operator==(const stopos_key &k) const;
    bool operator!=(const stopos_key &k) const;

    // to assign an unsigned integer value to a key
    template <typename T> void set(const T k)
      {
        this->value = "";
        this->tostring(this->value,k);
        return;
      }

    // to get the unsigned integer value from a key
    template <typename T> T get() const
    {
      T r = 0;

      for (unsigned int i=0; i<this->value.size(); i++)
        r = this->base*r + this->value[i]-this->firstchar;

      return r;
    }
};
#endif