1 #ifndef STAN_MATH_PRIM_FUN_AS_ARRAY_OR_SCALAR_HPP
2 #define STAN_MATH_PRIM_FUN_AS_ARRAY_OR_SCALAR_HPP
3
4 #include <stan/math/prim/fun/Eigen.hpp>
5 #include <stan/math/prim/meta.hpp>
6 #include <vector>
7
8 namespace stan {
9 namespace math {
10
11 /**
12 * Returns specified input value.
13 *
14 * @tparam T Type of element.
15 * @param v Specified value.
16 * @return Same value.
17 */
18 template <typename T, require_stan_scalar_t<T>* = nullptr>
as_array_or_scalar(T && v)19 inline T as_array_or_scalar(T&& v) {
20 return std::forward<T>(v);
21 }
22
23 /**
24 * Returns a reference to rvalue specified input value.
25 *
26 * @tparam T Type of element.
27 * @param v Specified value.
28 * @return Same value.
29 */
30 template <typename T, require_stan_scalar_t<T>* = nullptr>
as_array_or_scalar(T & v)31 inline T& as_array_or_scalar(T& v) {
32 return v;
33 }
34
35 /**
36 * Returns specified input value.
37 *
38 * @tparam T Type of element.
39 * @param v Specified value.
40 * @return Same value.
41 */
42 template <typename T, require_eigen_array_t<T>* = nullptr>
as_array_or_scalar(T && v)43 inline T as_array_or_scalar(T&& v) {
44 return std::forward<T>(v);
45 }
46
47 /**
48 * Converts a matrix type to an array.
49 *
50 * @tparam T Type of \c Eigen \c Matrix or expression
51 * @param v Specified \c Eigen \c Matrix or expression.
52 * @return Matrix converted to an array.
53 */
54 template <typename T, typename = require_eigen_t<T>,
55 require_not_eigen_array_t<T>* = nullptr>
as_array_or_scalar(T && v)56 inline auto as_array_or_scalar(T&& v) {
57 return make_holder([](auto& x) { return x.array(); }, std::forward<T>(v));
58 }
59
60 /**
61 * Converts a std::vector type to an array.
62 *
63 * @tparam T Type of scalar element.
64 * @param v Specified vector.
65 * @return Matrix converted to an array.
66 */
67 template <typename T, require_std_vector_t<T>* = nullptr,
68 require_not_std_vector_t<value_type_t<T>>* = nullptr>
as_array_or_scalar(T && v)69 inline auto as_array_or_scalar(T&& v) {
70 using T_map
71 = Eigen::Map<const Eigen::Array<value_type_t<T>, Eigen::Dynamic, 1>>;
72 return make_holder([](auto& x) { return T_map(x.data(), x.size()); },
73 std::forward<T>(v));
74 }
75
76 /**
77 * Converts an std::vector<std::vector> to an Eigen Array.
78 * @tparam T A standard vector with inner container of a standard vector
79 * with an inner stan scalar.
80 * @param v specified vector of vectorised
81 * @return An Eigen Array with dynamic rows and columns.
82 */
83 template <typename T, require_std_vector_vt<is_std_vector, T>* = nullptr,
84 require_std_vector_vt<is_stan_scalar, value_type_t<T>>* = nullptr>
as_array_or_scalar(T && v)85 inline auto as_array_or_scalar(T&& v) {
86 Eigen::Array<scalar_type_t<T>, -1, -1> ret(v.size(), v[0].size());
87 for (size_t i = 0; i < v.size(); ++i) {
88 ret.row(i) = Eigen::Map<const Eigen::Array<scalar_type_t<T>, 1, -1>>(
89 v[i].data(), v[i].size());
90 }
91 return ret;
92 }
93
94 } // namespace math
95 } // namespace stan
96
97 #endif
98