Implementation of n-ary sums and n-ary products.
The module "Data.SOP" is the main module of this library and contains
more detailed documentation.
The main use case of this package is to serve as the core of
A detailed description of the ideas behind this library is provided by
* Edsko de Vries and Andres Löh.
http://www.andres-loeh.de/TrueSumsOfProducts True Sums of Products
Workshop on Generic Programming (WGP) 2014.