public pure function disc_kernel(disc, coords) result(gamma_val)
Unnormalised smearing kernel of disc at coords: Gaussian in the
rotor-normal direction (delta_N), super-Gaussian (^8) in the radial
direction (delta_R) to give a flat-topped disc.
Nodes of different colours represent the following:
Solid arrows point from a procedure to one which it calls. Dashed
arrows point from an interface to procedures which implement that interface.
This could include the module procedures in a generic interface or the
implementation in a submodule of an interface in a parent module.
Where possible, edges connecting nodes are
given different colours to make them easier to distinguish in
large graphs.