check_unit_vector.hpp

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#ifndef STAN__MATH__ERROR_HANDLING__MATRIX__CHECK_UNIT_VECTOR_HPP
#define STAN__MATH__ERROR_HANDLING__MATRIX__CHECK_UNIT_VECTOR_HPP

#include <sstream>
#include <stan/math/matrix/Eigen.hpp>
#include <stan/math/error_handling/dom_err.hpp>
#include <stan/math/error_handling/matrix/constraint_tolerance.hpp>

namespace stan {

  namespace math {

    template <typename T_prob, typename T_result>
    bool check_unit_vector(const char* function,
                           const Eigen::Matrix<T_prob,Eigen::Dynamic,1>& theta,
                           const char* name,
                           T_result* result) {
      if (theta.size() == 0) {
        std::string message(name);
        message += " is not a valid unit vector. %1% elements in the vector.";
        return dom_err(function,0,name,
                       message.c_str(),"",
                       result);
      }
      T_prob ssq = theta.squaredNorm();
      if (!(fabs(1.0 - ssq) <= CONSTRAINT_TOLERANCE)) {
        std::stringstream msg;
        msg << "in function check_unit_vector(%1%), ";
        msg << name << " is not a valid unit vector.";
        msg << " The sum of the squares of the elements should be 1, but is " 
            << ssq;
        std::string tmp(msg.str());
        return dom_err(function,ssq,name,
                       tmp.c_str(),"",
                       result);
      }
      return true;
    }


    template <typename T>
    inline bool check_unit_vector(const char* function,
                                  const Eigen::Matrix<T,Eigen::Dynamic,1>& theta,
                                  const char* name,
                                  T* result = 0) {
      return check_unit_vector<T,T>(function,theta,name,result);
    }


  }
}
#endif