1 #ifndef STAN_MATH_PRIM_FUN_SEGMENT_HPP
2 #define STAN_MATH_PRIM_FUN_SEGMENT_HPP
3
4 #include <stan/math/prim/err.hpp>
5 #include <stan/math/prim/fun/Eigen.hpp>
6 #include <vector>
7
8 namespace stan {
9 namespace math {
10
11 /**
12 * Return the specified number of elements as a row/column vector starting
13 * from the specified element - 1 of the specified row/column vector.
14 *
15 * @tparam T type of the vector
16 */
17 template <typename Vec, require_vector_t<Vec>* = nullptr>
segment(const Vec & v,size_t i,size_t n)18 inline auto segment(const Vec& v, size_t i, size_t n) {
19 check_greater("segment", "n", i, 0.0);
20 check_less_or_equal("segment", "n", i, static_cast<size_t>(v.size()));
21 if (n != 0) {
22 check_greater("segment", "n", i + n - 1, 0.0);
23 check_less_or_equal("segment", "n", i + n - 1,
24 static_cast<size_t>(v.size()));
25 }
26 return v.segment(i - 1, n);
27 }
28
29 template <typename T>
segment(const std::vector<T> & sv,size_t i,size_t n)30 std::vector<T> segment(const std::vector<T>& sv, size_t i, size_t n) {
31 check_greater("segment", "i", i, 0.0);
32 check_less_or_equal("segment", "i", i, sv.size());
33 if (n != 0) {
34 check_greater("segment", "i+n-1", i + n - 1, 0.0);
35 check_less_or_equal("segment", "i+n-1", i + n - 1,
36 static_cast<size_t>(sv.size()));
37 }
38 std::vector<T> s;
39 for (size_t j = 0; j < n; ++j) {
40 s.push_back(sv[i + j - 1]);
41 }
42 return s;
43 }
44
45 } // namespace math
46 } // namespace stan
47
48 #endif
49