Install libghc-dual-tree-doc by entering the following commands in the terminal:
sudo apt update sudo apt install libghc-dual-tree-doc
Description:
Rose trees with cached and accumulating monoidal annotations; documentation
Rose (n-ary) trees with both upwards- (i.e. cached) and downwards-traveling (i.e. accumulating) monoidal annotations. . Abstractly, a DUALTree is a rose (n-ary) tree with data at leaves, data at internal nodes, and two types of monoidal annotations, one travelling "up" the tree and one traveling "down". . 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://hackage.haskell.org/package/dual-tree
Version: 0.2.1-1build2
Section: universe/doc