.. _program_listing_file_SeQuant_domain_mbpt_space_qns.hpp:

Program Listing for File space_qns.hpp
======================================

|exhale_lsh| :ref:`Return to documentation for file <file_SeQuant_domain_mbpt_space_qns.hpp>` (``SeQuant/domain/mbpt/space_qns.hpp``)

.. |exhale_lsh| unicode:: U+021B0 .. UPWARDS ARROW WITH TIP LEFTWARDS

.. code-block:: cpp

   //
   // Created by Eduard Valeyev on 3/9/25.
   //
   
   #ifndef SEQUANT_DOMAIN_MBPT_SPACE_QNS_HPP
   #define SEQUANT_DOMAIN_MBPT_SPACE_QNS_HPP
   
   #include "SeQuant/core/fwd.hpp"
   
   namespace sequant::mbpt {
   
   template <typename BitSet>
   struct mask;
   
   template <typename BitSet>
   constexpr auto mask_v = mask<BitSet>::value;
   
   template <typename BitSet>
   using mask_t = mask<BitSet>::type;
   
   // SeQuant/mbpt definitions of IndexSpace QNs
   
   enum class Spin : bitset_t {
     alpha = 0b000001,  
     beta = 0b000010,   
     any = alpha | beta,
     // syntactic sugar
     free = any,   
     none = any,   
     up = alpha,   
     down = beta,  
     // only used by legacy code
     null = 0b000000
   };
   
   template <>
   struct mask<Spin> {
     using type = std::underlying_type_t<Spin>;
     static constexpr type value = static_cast<type>(Spin::any);
   };
   
   enum class LCAOQNS : bitset_t {
     ao = 0b000100,
     pao = 0b001000  // projected AO space denotes unoccupied spaces made
                     // from AO basis and orthogonal to occupied orbitals
   };
   
   template <>
   struct mask<LCAOQNS> {
     using type = std::underlying_type_t<LCAOQNS>;
     static constexpr type value =
         static_cast<type>(LCAOQNS::ao) | static_cast<type>(LCAOQNS::pao);
   };
   
   enum class TensorFactorizationQNS : bitset_t {
     df = 0b010000,  // density fitting
     thc = 0b100000  // tensor hypercontraction
   };
   
   template <>
   struct mask<TensorFactorizationQNS> {
     using type = std::underlying_type_t<TensorFactorizationQNS>;
     static constexpr type value = static_cast<type>(TensorFactorizationQNS::df) |
                                   static_cast<type>(TensorFactorizationQNS::thc);
   };
   
   enum class BatchingQNS : bitset_t {
     batch = 0b1000000,  // for batching tensors
   };
   
   template <>
   struct mask<BatchingQNS> {
     using type = std::underlying_type_t<BatchingQNS>;
     static constexpr type value = static_cast<type>(BatchingQNS::batch);
   };
   
   }  // namespace sequant::mbpt
   
   #endif  // SEQUANT_DOMAIN_MBPT_SPACE_QNS_HPP