check_unit_vector.hpp

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#ifndef STAN_MATH_PRIM_ERR_CHECK_UNIT_VECTOR_HPP
#define STAN_MATH_PRIM_ERR_CHECK_UNIT_VECTOR_HPP
 
#include <stan/math/prim/fun/Eigen.hpp>
#include <stan/math/prim/meta.hpp>
#include <stan/math/prim/err/check_nonzero_size.hpp>
#include <stan/math/prim/err/constraint_tolerance.hpp>
#include <stan/math/prim/err/make_iter_name.hpp>
#include <stan/math/prim/err/throw_domain_error.hpp>
#include <stan/math/prim/fun/abs.hpp>
#include <stan/math/prim/fun/to_ref.hpp>
#include <stan/math/prim/fun/value_of_rec.hpp>
#include <sstream>
#include <string>
#include <cmath>
 
namespace stan {
namespace math {
 
template <typename Vec, require_vector_t<Vec>* = nullptr,
          require_not_std_vector_t<Vec>* = nullptr>
void check_unit_vector(const char* function, const char* name,
                       const Vec& theta) {
  check_nonzero_size(function, name, theta);
  using std::fabs;
  scalar_type_t<Vec> ssq = value_of_rec(theta).squaredNorm();
  if (!(fabs(1.0 - ssq) <= CONSTRAINT_TOLERANCE)) {
    [&]() STAN_COLD_PATH {
      std::stringstream msg;
      msg << "is not a valid unit vector."
          << " The sum of the squares of the elements should be 1, but is ";
      std::string msg_str(msg.str());
      throw_domain_error(function, name, ssq, msg_str.c_str());
    }();
  }
}
 
template <typename StdVec, require_std_vector_t<StdVec>* = nullptr>
void check_unit_vector(const char* function, const char* name,
                       const StdVec& theta) {
  for (size_t i = 0; i < theta.size(); ++i) {
    check_unit_vector(function, internal::make_iter_name(name, i).c_str(),
                      theta[i]);
  }
}
 
}  // namespace math
}  // namespace stan
#endif