Changes Necessary for Building the Fock Operator (#437)

* add density instantiations

* Committing clang-format changes

---------

Co-authored-by: github-actions[bot] <github-actions[bot]@users.noreply.github.com>

include/chemist/density/decomposable_density.hpp

@@ -15,7 +15,7 @@
  */
 
 #pragma once
-#include <chemist/density/density.hpp>
+#include <chemist/density/density_class.hpp>
 #include <chemist/quantum_mechanics/wavefunction/transformed.hpp>
 
 namespace chemist {
@@ -172,4 +172,6 @@ bool operator!=(const DecomposableDensity<LHSParticles...>& lhs,
 /// Type of the one-Electron density
 using Decomposable1EDensity = DecomposableDensity<Electron>;
 
+extern template class DecomposableDensity<Electron>;
+
 } // namespace chemist

include/chemist/density/density.hpp

@@ -1,5 +1,5 @@
 /*
- * Copyright 2022 NWChemEx-Project
+ * Copyright 2024 NWChemEx-Project
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -15,180 +15,6 @@
  */
 
 #pragma once
-#include <chemist/electron/electron.hpp>
-#include <chemist/quantum_mechanics/wavefunction/aos.hpp>
-#include <tensorwrapper/tensorwrapper.hpp>
-
-namespace chemist {
-
-/** @brief Class describing a density.
- *
- *  In Electronic structure theory we place a lot of emphasis on the
- *  one-Electron density; however, there are many other densities. This class
- *  is templated on the types and number of particles that the density
- *  describes. In turn this allows for this class to model densities involving
- *  an arbitrary number of arbitrary particles.
- *
- *  @note At the moment this class is basically a strong type which wraps a
- *        tensor and an AOs object.
- *
- *  @note If we want to support Particles... != Electron... we will need to add
- *        TMP to work out the basis type.
- *
- *  @tparam Particles The types of the particles described by this density. At
- *                    the moment the types are used purely for strong typing
- *                    purposes. Expected to be unqualified types.
- *
- */
-template<typename... Particles>
-class Density {
-public:
-    /// Type used to represent the numeric form of the density
-    using value_type = tensorwrapper::Tensor;
-
-    /// Type of a mutable reference to the density matrix
-    using reference = value_type&;
-
-    /// Type of a read-only reference to the density matrix
-    using const_reference = const value_type&;
-
-    /// Type of the basis set for value_type
-    using basis_type = wavefunction::AOs;
-
-    /// Type of a mutable reference to an object of type basis_type
-    using basis_reference = basis_type&;
-
-    /// Type of a read-only reference to an object of basis_type
-    using const_basis_reference = const basis_type&;
-
-    /// Default ctor
-    explicit Density() = default;
-
-    /** @brief Creates a new density object with the provided values.
-     *
-     *  @param[in] rho The tensor representation of the density matrix.
-     *  @param[in] orbs The basis set the density matrix is expressed in.
-     *
-     *  @throw None No throw guarantee.
-     */
-    Density(value_type rho, basis_type orbs) :
-      m_density_(std::move(rho)), m_orbs_(std::move(orbs)) {}
-
-    /** @brief Returns a mutable reference to the density matrix.
-     *
-     *  @return A mutable reference to the tensor representation of the density.
-     *
-     *  @throw None No throw guarantee.
-     */
-    reference value() noexcept { return m_density_; }
-
-    /** @brief Provides read-only access to the density matrix.
-     *
-     *  Same as the non-const version except that the return is read-only. See
-     *  description of non-const version for more details.
-     *
-     *  @return The density value.
-     *
-     *  @throw None No throw guarantee.
-     */
-    const_reference value() const noexcept { return m_density_; }
-
-    /** @brief Returns a mutable reference to the orbital basis set for the
-     *         density.
-     *
-     *  @return A mutable reference to the basis set for *this.
-     *
-     *  @throw None No throw guarantee.
-     */
-    basis_reference basis_set() noexcept { return m_orbs_; }
-
-    /** @brief Provides read-only access to the orbital basis set used to define
-     *         the density matrix.
-     *
-     *  Same as the non-const version except that the return is read-only. See
-     *  description of the non-const version for more details.
-     *
-     *  @return The orbital basis the density is formed in.
-     *
-     *  @throw ??? Throws if the derived class's implementation of `basis_set_`
-     *             throws. Same throw guarantee.
-     */
-    const_basis_reference basis_set() const { return basis_set_(); }
-
-protected:
-    /// The density tensor
-    value_type m_density_;
-
-    /// For assigning density value in derived types
-    explicit Density(value_type rho) : m_density_(rho) {}
-
-    /** @brief To be overridden by the derived class to implement basis_set().
-     *
-     *  The derived class is responsible for ensuring this function returns the
-     *  basis set.
-     *
-     *  @return The orbital basis the density is formed in.
-     *
-     *  @throw None No throw guarantee.
-     */
-    virtual const_basis_reference basis_set_() const { return m_orbs_; }
-
-private:
-    /// The orbital space used to make the density
-    basis_type m_orbs_;
-};
-
-/** @brief Compares two Density instances for equality.
- *
- *  @relates Density
- *
- *  Two Density instances are equal if they describe the same particles and they
- *  have the same numeric value.
- *
- *  @tparam LHSParticles The particle types for @p lhs.
- *  @tparam RHSParticles The particle types for @p rhs.
- *
- *  @param[in] lhs The density on the left side of the equality operator.
- *  @param[in] rhs The density on the right side of the equality operator.
- *
- *  @return True if @p lhs has the same type and numeric value as @p rhs. False
- *          otherwise.
- *
- *  @throw None No throw guarantee.
- */
-template<typename... LHSParticles, typename... RHSParticles>
-bool operator==(const Density<LHSParticles...>& lhs,
-                const Density<RHSParticles...>& rhs) {
-    if constexpr(std::is_same_v<decltype(lhs), decltype(rhs)>) {
-        return std::tie(lhs.basis_set(), lhs.value()) ==
-               std::tie(rhs.basis_set(), rhs.value());
-    } else {
-        return false;
-    }
-}
-
-/** @brief Determines if two Density instances are different.
- *
- *  @relates Density
- *
- *  Two Densities are different if the equality comparison returns false. This
- *  indicates that the densities either have different types and/or different
- *  numeric values.
- *
- *  @tparam LHSParticles The particle types for @p lhs.
- *  @tparam RHSParticles The particle types for @p rhs.
- *
- *  @param[in] lhs The density on the left side of the not-equal operator.
- *  @param[in] rhs The density on the right side of the not-equal operator.
- *
- *  @return False if @p lhs and @p rhs are equal and true otherwise.
- *
- *  @throw None No throw guarantee.
- */
-template<typename... LHSParticles, typename... RHSParticles>
-bool operator!=(const Density<LHSParticles...>& lhs,
-                const Density<RHSParticles...>& rhs) {
-    return !(lhs == rhs);
-}
-
-} // namespace chemist
+#include <chemist/density/decomposable_density.hpp>
+#include <chemist/density/density_class.hpp>
+#include <chemist/traits/density_traits.hpp>