Line data    Source code

       1           0 : // Distributed under the MIT License.
       2             : // See LICENSE.txt for details.
       3             : 
       4             : #pragma once
       5             : 
       6             : #include <type_traits>
       7             : 
       8             : #include "Utilities/Requires.hpp"
       9             : #include "Utilities/StlStreamDeclarations.hpp"
      10             : 
      11             : namespace tt {
      12             : /// @{
      13             : /// \ingroup TypeTraitsGroup
      14             : /// \brief Check if type `T` has operator<<(`S`, `T`) defined.
      15             : ///
      16             : /// \details
      17             : /// Inherits from std::true_type if the type `T` has operator<<(`S`, `T`)
      18             : /// defined for a stream `S`, otherwise inherits from std::false_type
      19             : ///
      20             : /// \usage
      21             : /// For any type `T` and stream type `S`,
      22             : /// \code
      23             : /// using result = tt::is_streamable<S, T>;
      24             : /// \endcode
      25             : ///
      26             : /// \metareturns
      27             : /// std::bool_constant
      28             : ///
      29             : /// \semantics
      30             : /// If the type `T` has operator<<(`S`, `T`) defined for stream `S`, then
      31             : /// \code
      32             : /// typename result::type = std::true_type;
      33             : /// \endcode
      34             : /// otherwise
      35             : /// \code
      36             : /// typename result::type = std::false_type;
      37             : /// \endcode
      38             : ///
      39             : /// \example
      40             : /// \snippet Test_IsStreamable.cpp is_streamable_example
      41             : /// \see std::cout std::ifstream std::sstream std::ostream
      42             : /// \tparam S the stream type, e.g. std::stringstream or std::ostream
      43             : /// \tparam T the type we want to know if it has operator<<
      44             : template <typename S, typename T, typename = std::void_t<>>
      45           1 : struct is_streamable : std::false_type {};
      46             : 
      47             : /// \cond
      48             : template <typename S, typename T>
      49             : struct is_streamable<
      50             :     S, T,
      51             :     std::void_t<decltype(std::declval<std::add_lvalue_reference_t<S>>()
      52             :                          << std::declval<T>()),
      53             :                 Requires<not std::is_same<S, T>::value>>> : std::true_type {};
      54             : /// \endcond
      55             : 
      56             : /// \see is_streamable
      57             : template <typename S, typename T>
      58           1 : constexpr bool is_streamable_v = is_streamable<S, T>::value;
      59             : 
      60             : /// \see is_streamable
      61             : template <typename S, typename T>
      62           1 : using is_streamable_t = typename is_streamable<S, T>::type;
      63             : /// @}
      64             : }  // namespace tt