text: #include "pwl_slab.h"
  
  SlabMappingFE_PWL::
  SlabMappingFE_PWL(const chi_mesh::CellSlab &slab_cell,
                    const chi_mesh::MeshContinuumPtr &ref_grid,
                    const chi_math::QuadratureGaussLegendre &minumum_volume_quadrature,
                    const chi_math::QuadratureGaussLegendre &arb_volume_quadrature) :
    CellMappingFE_PWL(2, ref_grid),
    default_volume_quadrature(minumum_volume_quadrature),
    arbitrary_volume_quadrature(arb_volume_quadrature)
  {
    grid = ref_grid;
    v0i = slab_cell.vertex_ids[0];
    v1i = slab_cell.vertex_ids[1];
    v0 = *grid->vertices[v0i];
    chi_mesh::Vertex v1 = *grid->vertices[v1i];
  
    chi_mesh::Vector3 v01 = v1 - v0;
    h = v01.Norm();
  
    face_dof_mappings.emplace_back(1,0);
    face_dof_mappings.emplace_back(1,1);
  
    normals[0] = slab_cell.faces[0].normal;
    normals[1] = slab_cell.faces[1].normal;
  }