multiindex.hh

#ifndef MULTI_INDEX_HH
#define MULTI_INDEX_HH

#include <vector>

/** \brief A multi-index
 */
class MultiIndex
  : public std::vector<unsigned int>
{

  // The range of each component
  unsigned int limit_;

public:
  /** \brief Constructor with a given range for each digit
   * \param n Number of digits
   */
  MultiIndex(unsigned int n, unsigned int limit)
    : std::vector<unsigned int>(n),
    limit_(limit)
  {
    std::fill(this->begin(), this->end(), 0);
  }

  /** \brief Increment the MultiIndex */
  MultiIndex& operator++() {

    for (size_t i=0; i<size(); i++) {

      // Augment digit
      (*this)[i]++;

      // If there is no carry-over we can stop here
      if ((*this)[i]<limit_)
        break;

      (*this)[i] = 0;

    }
    return *this;
  }

  /** \brief Compute how many times you can call operator++ before getting to (0,...,0) again */
  size_t cycle() const {
    size_t result = 1;
    for (size_t i=0; i<size(); i++)
      result *= limit_;
    return result;
  }

};

#endif