Install libghc-exact-pi-doc by entering the following commands in the terminal:
sudo apt update sudo apt install libghc-exact-pi-doc
Description:
Exact rational multiples of pi (and integer powers of pi); documentation
Provides an exact representation for rational multiples of pi alongside an approximate representation of all reals. Useful for storing and computing with conversion factors between physical units. . This package provides the documentation for a library for the Haskell programming language. See http://www.haskell.org/ for more information on Haskell.
Homepage: https://github.com/dmcclean/exact-pi/
Version: 0.4.1.2-3build1
Section: universe/doc