SOP extras

These packages extend the SOP ecosystem with other types that follow the same principles. In particular:

• strict-sop-core provides strict alternatives to the NS and NP types defined in sop-core.
• sop-extras define new types that complement the standard SOP definitions:
  • Index for indexing into a type-level list and project an NP by index or inject in an NS by index,
  • InPairs for functions on contiguous pairs of types in a type-level list,
  • Tails for functions from a type to all the later types in a type-level list,
  • Telescope for an NS that can be extended or retracted to other summands, plus keeping some information for preceding types in the type-level list.

These definitions have had very little variations in a long time, and therefore the vast majority of the code was an invention of the original authors who we credit here: Edsko de Vries and Thomas Winant.