Install libghc-gtk3-doc by entering the following commands in the terminal:
sudo apt update sudo apt install libghc-gtk3-doc
Description:
binding to the Gtk+ graphical user interface library; documentation
This is the core library of the Gtk2Hs suite of libraries for Haskell based on Gtk+. Gtk+ is an extensive and mature multi-platform toolkit for creating graphical user interfaces. . 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://projects.haskell.org/gtk2hs/
Version: 0.14.8-1build1
Section: universe/doc