move is_tuple back to stan::math namespace

Author: SteveBronder

stan/math/prim/fun/promote_scalar.hpp

@@ -2,8 +2,8 @@
 #define STAN_MATH_PRIM_FUN_PROMOTE_SCALAR_HPP
 
 #include <stan/math/prim/fun/Eigen.hpp>
-#include <stan/math/prim/meta.hpp>
 #include <stan/math/prim/functor/apply.hpp>
+#include <stan/math/prim/meta.hpp>
 #include <vector>
 #include <tuple>
 #include <type_traits>

stan/math/prim/meta/contains_tuple.hpp

@@ -7,7 +7,7 @@ namespace stan {
 namespace internal {
 template <typename T>
 struct contains_tuple_impl {
-  static constexpr bool value = stan::is_tuple_v<T>;
+  static constexpr bool value = stan::math::is_tuple_v<T>;
 };
 
 template <typename T, typename... VecArgs>

stan/math/prim/meta/is_tuple.hpp

@@ -6,6 +6,7 @@
 #include <type_traits>
 
 namespace stan {
+namespace math {
 namespace internal {
 
 template <typename... Types>
@@ -20,7 +21,6 @@ struct is_tuple : internal::is_tuple_impl<std::decay_t<T>> {};
 
 template <typename T>
 constexpr bool is_tuple_v = is_tuple<T>::value;
-
 /*! \ingroup require_std */
 /*! \defgroup tuple_types tuple  */
 /*! \addtogroup tuple_types */
@@ -47,6 +47,7 @@ template <typename... Types>
 using require_all_not_tuple_t
     = require_all_not_t<is_tuple<std::decay_t<Types>>...>;
 /*! @} */
+}
 
 }  // namespace stan
 

stan/math/rev/meta/arena_type.hpp

@@ -49,20 +49,6 @@ struct arena_type_impl<
   using type = plain_type_t<T>;
 };
 
-template <typename T, typename = void>
-struct arena_tuple_impl {};
-
-template <typename T>
-struct arena_tuple_impl<T, stan::require_not_tuple_t<T>> {
-  using type = typename internal::arena_type_impl<std::decay_t<T>>::type;
-};
-
-template <typename... Types>
-struct arena_tuple_impl<std::tuple<Types...>> {
-  using type = std::tuple<
-      typename internal::arena_tuple_impl<std::decay_t<Types>>::type...>;
-};
-
 }  // namespace internal
 
 /**
@@ -73,10 +59,6 @@ struct arena_tuple_impl<std::tuple<Types...>> {
 template <typename T>
 using arena_t = typename internal::arena_type_impl<std::decay_t<T>>::type;
 
-template <typename T>
-using arena_tuple_t =
-    typename internal::arena_tuple_impl<std::decay_t<T>>::type;
-
 }  // namespace stan
 
 #endif

test/unit/math/mix/util.hpp

@@ -30,7 +30,7 @@ inline double get_val(T&& x) {
  */
 template <typename F, typename... Types>
 inline void recursive_for_each(F&& f, Types&&... args) {
-  if constexpr (std::conjunction_v<stan::is_tuple<Types>...>) {
+  if constexpr (std::conjunction_v<stan::math::is_tuple<Types>...>) {
     stan::math::for_each(
         [&f](auto&&... args_i) { recursive_for_each(f, args_i...); }, args...);
   } else {

test/unit/math/prim/meta/is_tuple_test.cpp

@@ -4,9 +4,9 @@
 #include <vector>
 
 TEST(MathMetaPrim, is_tuple) {
-  EXPECT_TRUE((stan::is_tuple<std::tuple<double>>::value));
-  EXPECT_TRUE((stan::is_tuple<std::tuple<double>&>::value));
-  EXPECT_TRUE((stan::is_tuple<std::tuple<double>&&>::value));
-  EXPECT_FALSE((stan::is_tuple<double>::value));
-  EXPECT_FALSE((stan::is_tuple<std::vector<double>>::value));
+  EXPECT_TRUE((stan::math::is_tuple<std::tuple<double>>::value));
+  EXPECT_TRUE((stan::math::is_tuple<std::tuple<double>&>::value));
+  EXPECT_TRUE((stan::math::is_tuple<std::tuple<double>&&>::value));
+  EXPECT_FALSE((stan::math::is_tuple<double>::value));
+  EXPECT_FALSE((stan::math::is_tuple<std::vector<double>>::value));
 }