utils/basis.hh

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// SPDX-FileCopyrightText: 2021-2024 The Ikarus Developers mueller@ibb.uni-stuttgart.de
// SPDX-License-Identifier: LGPL-3.0-or-later
 
#pragma once
 
#include <utility>
 
#include <dune/functions/functionspacebases/defaultglobalbasis.hh>
 
#include <ikarus/utils/flatprebasis.hh>
 
namespace Ikarus {
 
  template <typename PreBasis_>
  class Basis {
  public:
    using PreBasis = PreBasis_;                    
    using GridView = typename PreBasis::GridView;  
    using UntouchedBasis
        = decltype(Dune::Functions::DefaultGlobalBasis(std::declval<PreBasis>()));  
    using FlatBasis = decltype(Dune::Functions::DefaultGlobalBasis(
        Ikarus::flatPreBasis(std::declval<PreBasis>())));  
 
    explicit Basis(const PreBasis& pb)
        : bb{Dune::Functions::DefaultGlobalBasis(pb)},
          fb{Dune::Functions::DefaultGlobalBasis(Ikarus::flatPreBasis(pb))} {}
 
    auto& flat() { return fb; }
 
    auto& untouched() { return bb; }
 
    const auto& flat() const { return fb; }
 
    const auto& untouched() const { return bb; }
 
    const auto& gridView() const { return bb.gridView(); }
 
    auto& gridView() { return bb.gridView(); }
 
  private:
    UntouchedBasis bb;
    FlatBasis fb;
  };
 
  template <typename GridView, typename PreBasisFactory>
  auto makeBasis(const GridView& gv, const PreBasisFactory& pb) {
    auto preBasis = pb(gv);
    return Basis(preBasis);
  }
 
  template <typename PreBasis>
  auto makeBasis(const Dune::Functions::DefaultGlobalBasis<PreBasis>& gb) {
    return Basis(gb.preBasis());
  }
}  // namespace Ikarus