.. _program_listing_file_src_pcms_field_element_dispatch.h:

Program Listing for File element_dispatch.h
===========================================

|exhale_lsh| :ref:`Return to documentation for file <file_src_pcms_field_element_dispatch.h>` (``src/pcms/field/element_dispatch.h``)

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

.. code-block:: cpp

   #ifndef PCMS_FIELD_ELEMENT_DISPATCH_H
   #define PCMS_FIELD_ELEMENT_DISPATCH_H
   
   #include "pcms/utility/assert.h"
   #include <string>
   #include <type_traits>
   
   namespace pcms::detail
   {
   
   // Runtime -> compile-time bridge for finite-element order.
   //
   // Turns a runtime Lagrange order into a compile-time std::integral_constant and
   // invokes the generic callable `f` with it, so the callee can instantiate
   // order-templated kernels (shape functions, DOF-per-element counts) without
   // scattering `if (order == ...)` branches through device code. This is the same
   // dispatch shape as MakeMeshFieldBackend's switch, factored out so both the
   // transfer integrators and the MeshField evaluator backend can share it.
   //
   // Supported orders: 0 (one DOF per element) and 1 (one DOF per vertex). Add a
   // case here when a higher-order element (P2, ...) lands; every consumer picks
   // it up at once. `f` must return the same type for every supported order.
   template <typename F>
   auto DispatchByOrder(int order, F&& f)
   {
     switch (order) {
       case 0: return f(std::integral_constant<int, 0>{});
       case 1: return f(std::integral_constant<int, 1>{});
       default:
         throw pcms_error("DispatchByOrder: unsupported element order " +
                          std::to_string(order));
     }
   }
   
   } // namespace pcms::detail
   
   #endif // PCMS_FIELD_ELEMENT_DISPATCH_H