cumulative_sum.hpp

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#ifndef STAN__MATH__MATRIX__CUMULATIVE_SUM_HPP
#define STAN__MATH__MATRIX__CUMULATIVE_SUM_HPP

#include <vector>
#include <stan/math/matrix/Eigen.hpp>

namespace stan {
  namespace math {

    template <typename T>
    inline std::vector<T>
    cumulative_sum(const std::vector<T>& x) {
      std::vector<T> result(x.size());
      if (x.size() == 0)
        return result;
      result[0] = x[0];
      for (size_t i = 1; i < result.size(); ++i)
        result[i] = x[i] + result[i-1];
      return result;
    }
    
    template <typename T, int R, int C>
    inline Eigen::Matrix<T,R,C> 
    cumulative_sum(const Eigen::Matrix<T,R,C>& m) {
      Eigen::Matrix<T,R,C> result(m.rows(),m.cols());
      if (m.size() == 0)
        return result;
      result(0) = m(0);
      for (int i = 1; i < result.size(); ++i)
        result(i) = m(i) + result(i-1);
      return result;
    }
  }
}
#endif