The MPQC code is organized into a hierarchy of C++ namespaces, as described below:

Each of these namespaces is indended to contain the functionality needed for all users of MPQC libraries. The code indended only for advanced users should be placed in the nested utility namespace. For example, the package-wide functionality that is intended only for advanced users should go into mpqc::utility. Similarly, the advanced functionality related to the Gaussian AO representation should go to mpqc::lcao::gaussian::utility.

Similarly, the implementation details of the code in each namespace that are not intended for any users of MPQC should go into the nested detail namespace, e.g. mpqc::lcao::gaussian::detail should contain the implementation details of classes in mpqc::lcao::gaussian.

When adding or reogranizing code you should adhere to a set of guidelines to decide which namespace should be chosen for a given variable, function, or class.

• Most of the MPQC code should be placed into one of namespaces contained in namespace mpqc ; the global namespace should not be used.
• The top-level mpqc namespace should contain the unique functionality that is likely to be used by every user of the MPQC libraries. This includes for example the mpqc::Energy class as well as all exception classes. Note that this does not include classes that implement electronic structure methods that could have multiple implementations that e.g. use different numerical representations; to avoid having two DFT classes, one based on LCAO and another based on the finite-difference/finite-element representation each should go into the nested namespace for that numerical representation.
• All LCAO-based code should be placed in the mpqc::lcao namespace. Although in chemistry we almost exclusively use Gaussians, it is recommended that Gaussian-specific code is placed in the mpqc::lcao::gaussian subspace (this is only partially implemented) so that it is possible to re-use the LCAO technology in non-Gaussian contexts, e.g. with model Hamiltonians.
• Most of the code located under src/mpqc/math should live in mpqc::math namespace.
• Most of the code located under src/mpqc/util should live in mpqc::utility namespace.