Add unified batch traits

`xsimd::batch_traits` with mask type, scalar type, and some properties
for scalar, `batch`, and `batch_bool`.

Author: kalenedrael

docs/source/api/type_traits.rst

@@ -32,9 +32,15 @@ Type Traits
 ===========
 
 `xsimd` provides a few type traits to interact with scalar and batch types in an
-uniformeous manner.
+uniform manner.
 
 
+Combined traits:
+
++---------------------------------------+----------------------------------------------------+
+| :cpp:class:`batch_traits`             | batch types and proprties                          |
++---------------------------------------+----------------------------------------------------+
+
 Type check:
 
 +---------------------------------------+----------------------------------------------------+

include/xsimd/types/xsimd_traits.hpp

@@ -233,59 +233,133 @@ namespace xsimd
     /**
      * @ingroup batch_traits
      *
-     * type traits that inherits from @c std::true_type for @c batch<...> types and from
-     * @c std::false_type otherwise.
+     * type traits that provide information about a batch or scalar type.
      *
      * @tparam T type to analyze.
      */
+
     template <class T>
-    struct is_batch;
+    struct batch_traits
+    {
+        using scalar_type = T; ///< T if scalar, or type of the scalar element for the batch T.
+        using mask_type = bool; ///< Mask type for T: bool for scalars, or batch_bool for batch types.
 
+        static constexpr bool is_batch = false; ///< True if T is @c batch<...>.
+        static constexpr bool is_batch_bool = false; ///< True if T is @c batch_bool<...>.
+        static constexpr bool is_any_batch = false; ///< True if T is @c batch<...> or @c batch_bool<...>.
+        static constexpr bool is_complex = detail::is_complex<T>::value; ///< True if T is complex or a batch of complex values.
+    };
+
+#if __cplusplus < 201703L
+    template <class T>
+    constexpr bool batch_traits<T>::is_batch;
     template <class T>
-    struct is_batch : std::false_type
+    constexpr bool batch_traits<T>::is_batch_bool;
+    template <class T>
+    constexpr bool batch_traits<T>::is_any_batch;
+    template <class T>
+    constexpr bool batch_traits<T>::is_complex;
+#endif
+
+    template <class T, class A>
+    struct batch_traits<batch<T, A>>
     {
+        using scalar_type = T;
+        using mask_type = typename batch<T, A>::batch_bool_type;
+
+        static constexpr bool is_batch = true;
+        static constexpr bool is_batch_bool = false;
+        static constexpr bool is_any_batch = true;
+        static constexpr bool is_complex = detail::is_complex<T>::value;
     };
 
+#if __cplusplus < 201703L
+    template <class T, class A>
+    constexpr bool batch_traits<batch<T, A>>::is_batch;
+    template <class T, class A>
+    constexpr bool batch_traits<batch<T, A>>::is_batch_bool;
+    template <class T, class A>
+    constexpr bool batch_traits<batch<T, A>>::is_any_batch;
+    template <class T, class A>
+    constexpr bool batch_traits<batch<T, A>>::is_complex;
+#endif
+
     template <class T, class A>
-    struct is_batch<batch<T, A>> : std::true_type
+    struct batch_traits<batch_bool<T, A>>
     {
+        using scalar_type = bool;
+        using mask_type = batch_bool<T, A>;
+
+        static constexpr bool is_batch = false;
+        static constexpr bool is_batch_bool = true;
+        static constexpr bool is_any_batch = true;
+        static constexpr bool is_complex = false;
     };
 
+#if __cplusplus < 201703L
+    template <class T, class A>
+    constexpr bool batch_traits<batch_bool<T, A>>::is_batch;
+    template <class T, class A>
+    constexpr bool batch_traits<batch_bool<T, A>>::is_batch_bool;
+    template <class T, class A>
+    constexpr bool batch_traits<batch_bool<T, A>>::is_any_batch;
+    template <class T, class A>
+    constexpr bool batch_traits<batch_bool<T, A>>::is_complex;
+#endif
+
     /**
      * @ingroup batch_traits
      *
-     * type traits that inherits from @c std::true_type for @c batch_bool<...> types and from
+     * type traits that inherits from @c std::true_type for @c batch<...> types and from
      * @c std::false_type otherwise.
      *
      * @tparam T type to analyze.
      */
 
     template <class T>
-    struct is_batch_bool : std::false_type
+    struct is_batch : std::integral_constant<bool, batch_traits<T>::is_batch>
     {
     };
 
-    template <class T, class A>
-    struct is_batch_bool<batch_bool<T, A>> : std::true_type
+    /**
+     * @ingroup batch_traits
+     *
+     * type traits that inherits from @c std::true_type for @c batch_bool<...> types and from
+     * @c std::false_type otherwise.
+     *
+     * @tparam T type to analyze.
+     */
+
+    template <class T>
+    struct is_batch_bool : std::integral_constant<bool, batch_traits<T>::is_batch_bool>
     {
     };
 
     /**
      * @ingroup batch_traits
      *
-     * type traits that inherits from @c std::true_type for @c batch<std::complex<...>>
+     * type traits that inherits from @c std::true_type for @c batch<...> or batch_bool<...>
      * types and from @c std::false_type otherwise.
      *
      * @tparam T type to analyze.
      */
 
     template <class T>
-    struct is_batch_complex : std::false_type
+    struct is_any_batch : std::integral_constant<bool, batch_traits<T>::is_any_batch>
     {
     };
 
-    template <class T, class A>
-    struct is_batch_complex<batch<std::complex<T>, A>> : std::true_type
+    /**
+     * @ingroup batch_traits
+     *
+     * type traits that inherits from @c std::true_type for @c batch<std::complex<...>>
+     * types and from @c std::false_type otherwise.
+     *
+     * @tparam T type to analyze.
+     */
+
+    template <class T>
+    struct is_batch_complex : std::integral_constant<bool, batch_traits<T>::is_batch && batch_traits<T>::is_complex>
     {
     };
 
@@ -300,12 +374,7 @@ namespace xsimd
     template <class T>
     struct scalar_type
     {
-        using type = T;
-    };
-    template <class T, class A>
-    struct scalar_type<batch<T, A>>
-    {
-        using type = T;
+        using type = typename batch_traits<T>::scalar_type;
     };
 
     template <class T>
@@ -322,12 +391,7 @@ namespace xsimd
     template <class T>
     struct mask_type
     {
-        using type = bool;
-    };
-    template <class T, class A>
-    struct mask_type<batch<T, A>>
-    {
-        using type = typename batch<T, A>::batch_bool_type;
+        using type = typename batch_traits<T>::mask_type;
     };
 
     template <class T>
@@ -364,7 +428,6 @@ namespace xsimd
     }
     template <typename T>
     using widen_t = typename detail::widen<T>::type;
-
 }
 
 #endif