Operads-0.2: Math/Operad/PPrint.hs

-- Copyright 2009 Mikael Vejdemo Johansson <mik@stanford.edu>
-- Released under a BSD license

-- | Pretty printing for user interaction.

module Math.Operad.PPrint where

import Data.List (intercalate)

-- * Pretty printing

-- | This yields user interface functions for human readable printing of objects.
-- The idea is to use 'Show' instances for marshalling of data, and 'PPrint' for
-- user interaction.
class PPrint a where
    pp :: a -> String
    pP :: a -> IO ()
    pP = putStrLn . pp

instance (PPrint a) => PPrint [a] where
    pp rs = "[" ++ (intercalate ",\n" (map pp rs)) ++ "]"

instance (PPrint a, PPrint b) => PPrint (a,b) where
    pp (r,t) = "(" ++ pp r ++ "," ++ pp t ++ ")"