Install libghc-either-doc by entering the following commands in the terminal:
sudo apt update sudo apt install libghc-either-doc
Description:
Either monad transformer; documentation
This library provides a minimalist Either monad transformer, EitherT. EitherT is a version of ErrorT that does not require a spurious Error instance for the Left case. . This package provides the documentation for a library for the Haskell programming language. See http://www.haskell.org/ for more information on Haskell.
Homepage: http://github.com/ekmett/either/
Version: 4.4.1.1-4build2
Section: universe/doc