Installing the PGF run-time library → Example 2: a question-answering system

Generated Haskell Code

• module Arithmetic where
  
  data GAnswer   = GNo | GYes 
  
  data GObject   = GNumber GInt 
  
  data GQuestion = GEven  GObject 
                 | GOdd   GObject 
                 | GPrime GObject 
  
  class Gf a where
    gf :: a -> Tree
    fg :: Tree -> a

• Also includes instances in the Gf class for the data types. See Arithmetic.hs.