New major features in this release: Better support for user-defined scalar types in expression. In particular, it is now possible to use integer-like and rational-like numeric types. Possible incompatibility of a scalar type with a certain algebra generator (e.g. spin operators vs an integer scalar) is checked at runtime. This is achieved by storing the structure constants of the algebra in the tagged union type var_number, which retains information about the category of the stored value (integer, rational or floating point). The compatibility is then checked in the trait method scalar_traits::make_const(var_number const& vn). Added optional support for boost::rational and GMP C++ types mpz_class, mpq_class, mpf_class as ScalarType. generator and derived classes no longer use the 'virtual copy-constructor' pattern: The virtual clone() method has been removed. Instead, generator is now derived from std::enable_shared_from_this, and instances of the generator classes are managed by shared pointers. This change leads to significant memory savings and speedups when working with long expressions. Introduction of sparse Hilbert spaces. A sparse Hilbert space contains at least one elementary space with a non-power-of-two dimension (for example, the state space of an S = 1 spin). This change is reflected in the API: New pure virtual method elementary_space::dim() and its implementation in derived classes. New method hilbert_space::is_sparse(). New method hilbert_space::vec_size() that returns the minimal size of a state vector compatible with this Hilbert space. The returned size is always a power of 2. Semantics of the existing method hilbert_space::dim() has been changed: Now it returns the exact dimension of the Hilbert space, which is smaller than hilbert_space::vec_size() if the Hilbert space is sparse. The free function foreach(hilbert_space const& hs, Functor&& f) now iterates over only the physical basis states instead of allhs.vec_size() basis state indices. New class compressed_state_view. It implements a view of a compressed state vector (continuous array) storing only the amplitudes corresponding to the physical basis states of a sparse Hilbert space. Dimension of elementary_space_boson had to be a power of 2. This restriction is lifted. Arguments of its constructor and ofmake_space_boson() have been adjusted accordingly. n_fermion_sector_view and n_fermion_multisector_view are now parameterized on the type of ranking algorithm used to map basis state indices from a full Hilbert space to a sector. Supported ranking algorithms are combination_ranking (selected by default), staggered_ranking and trie_ranking. All three algorithms are described in M. Wallerberger, K. Held, Phys. Rev. Research 4, 033238 (2022). Changed space_partition to store a constant reference to the Hilbert space being partitioned. This change is necessary to enable support for the sparse hilbert_space objects. space_partition is now templated on the Hilbert space type, whereas its constructors are not. Whenever possible, use compiler intrinsics to speed up complex bit manipulation operations (popcount, tzcount, pdep, pext). Improved performance and stability of space_partition::merge_subspaces() by switching to a non-recursive variant of the algorithm. A conda package is now being provided. For an exhaustive list of changes see the Changelog.