head.hpp

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#ifndef STAN_MATH_PRIM_FUN_HEAD_HPP
#define STAN_MATH_PRIM_FUN_HEAD_HPP
 
#include <stan/math/prim/err.hpp>
#include <stan/math/prim/fun/Eigen.hpp>
#include <vector>
 
namespace stan {
namespace math {
 
template <typename T, require_vector_t<T>* = nullptr>
inline auto head(const T& v, size_t n) {
  if (n != 0) {
    check_vector_index("head", "n", v, n);
  }
  return v.head(n);
}
 
template <typename T>
std::vector<T> head(const std::vector<T>& sv, size_t n) {
  if (n != 0) {
    check_std_vector_index("head", "n", sv, n);
  }
 
  std::vector<T> s(sv.begin(), sv.begin() + n);
  return s;
}
 
}  // namespace math
}  // namespace stan
 
#endif