.. _program_listing_file_SeQuant_domain_mbpt_vac_av.hpp:

Program Listing for File vac_av.hpp
===================================

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

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

.. code-block:: cpp

   //
   // Created by Eduard Valeyev on 2023-10-30.
   //
   using namespace sequant::mbpt;
   
   inline std::vector<std::pair<mbpt::OpType, mbpt::OpType>>
   default_op_connections() {
     using mbpt::OpType;
     static const std::vector<std::pair<mbpt::OpType, mbpt::OpType>> defaults = {
         {OpType::h, OpType::t},
         {OpType::f, OpType::t},
         {OpType::f̃, OpType::t},
         {OpType::g, OpType::t},
         // NBs
         // - for unitary ansatz can also connect t^+ with Hamiltonian
         // - for exact (non-approximated) unitary ansatz will also need to connect
         // t^+ with t;
         //   for MR unitary ansatz can also connect t with t and t^+ with t^+ ,
         //   but since adjoint() does not change OpType all of these are expressed
         //   as same connection ... this points out the need to have a separate
         //   OpType for t^+ and t, and in general the contents of OpType must be
         //   customizable
         {OpType::t, OpType::h},
         {OpType::t, OpType::f},
         {OpType::t, OpType::f̃},
         {OpType::t, OpType::g}};
     return defaults;
   }
   
   inline std::vector<std::pair<mbpt::OpType, mbpt::OpType>> concat(
       const std::vector<std::pair<mbpt::OpType, mbpt::OpType>> connections1,
       const std::vector<std::pair<mbpt::OpType, mbpt::OpType>> connections2) {
     return ranges::concat_view(connections1, connections2) | ranges::to_vector;
   }
   
   inline std::vector<std::pair<std::wstring, std::wstring>> to_label_connections(
       const std::vector<std::pair<mbpt::OpType, mbpt::OpType>>& op_connections) {
     // convert mbpt::OpType to std::wstring
     using mbpt::optype2label;
     std::vector<std::pair<std::wstring, std::wstring>> op_connect_wstr;
     for (const auto& [op1, op2] : op_connections) {
       op_connect_wstr.emplace_back(optype2label.at(op1), optype2label.at(op2));
     }
     return op_connect_wstr;
   }
   
   inline ExprPtr lower_to_tensor_form(ExprPtr& expr) {
     auto op_lowerer = [](ExprPtr& leaf) {
       if (leaf.is<op_t>()) leaf = leaf.as<op_t>().tensor_form();
     };
     expr->visit(op_lowerer, /* atoms only = */ true);
     return expr;
   }
   
   inline ExprPtr lower_to_tensor_form(const ExprPtr& expr_inp) {
     auto expr = expr_inp->clone();
     lower_to_tensor_form(expr);
     return expr;
   }
   
   
   ExprPtr vac_av(ExprPtr expr,
                  std::vector<std::pair<mbpt::OpType, mbpt::OpType>>
                      op_connections = default_op_connections(),
                  bool skip_clone = false);
   
   
   ExprPtr vac_av(
       ExprPtr expr,
       std::vector<std::pair<std::wstring, std::wstring>> op_connections,
       bool skip_clone = false);