Function cdshealpix::neighbour

pub fn neighbour(base_cell: u8, direction: MainWind) -> Option<u8>

Compute the base cell value which is the neighbour of the given base cell, in the given direction.
There is no neighbour:

• in the North and South directions for the equatorial region cells (i.e. cells 4, 5, 6 and 7)
• in the East and West directions for:
  • the north polar cap cells (i.e. cells 0, 1, 2 and 3)
  • the south polar cap cells (i.e. cells 8, 9, 10 and 11)