## `pretty-ghci` [![Travis Status][0]][1] [![Appveyor Status][4]][5] [![Hackage][2]][3]

This library will make your GHCi experience colourful in 3 steps:

  1. Install the executable globally with `cabal v2-install pretty-ghci`

  2. Modify your `~/.ghc/ghci.conf`

     ```haskell
     :set prompt      "λ> "
     :set prompt-cont "|> "

     -- Typing `:pretty` will turn on the pretty-printing
     :set -package process
     :{
     :def pretty \_ -> pure $ unlines $
       [ ":{"
       , "let pprint x = System.Process.withCreateProcess cp' $ \\(Just i) _ _ ph -> do"
       , "        System.IO.hPutStrLn i (show x)"
       , "        System.IO.hClose i"
       , "        _ <- System.Process.waitForProcess ph"
       , "        pure ()"
       , "      where cp = System.Process.proc \"pp-ghci\" [\"--value\", \"--smarter-layout\"]"
       , "            cp' = cp{ System.Process.std_out = System.Process.Inherit"
       , "                    , System.Process.std_err = System.Process.Inherit"
       , "                    , System.Process.std_in  = System.Process.CreatePipe }"
       , ":}"
       , ":set -interactive-print pprint"
       ]
     :}

     -- Typing `:no-pretty` will turn off the pretty-printing
     :def no-pretty \_ -> pure (":set -interactive-print System.IO.print")

     -- Make things pretty by default!
     :pretty
     ```

  3. Enjoy!

## Advantages over existing alternatives

  * One stop-solution for formatting and coloring with a small dependency graph
  * Takes your terminal width into account during the layout step
  * Works for values whose `Show` instance don't produce valid Haskell (ex: `Show (->)`)
  * Handles unboxed literals (ex: `MyTriple 1# 2.0# "hello"#`)
  * Your output will be coloured according to its lexical structure even if parsing fails
  * Install one global executable, not one library per GHC version
  * Works in `cabal repl` (although you need to call `:pretty` once at the start)

[0]: https://travis-ci.org/harpocrates/pretty-ghci.svg?branch=master
[1]: https://travis-ci.org/harpocrates/pretty-ghci
[2]: https://img.shields.io/hackage/v/pretty-ghci.svg
[3]: https://hackage.haskell.org/package/pretty-ghci
[4]: https://ci.appveyor.com/api/projects/status/qnbk7jblij7skb3l/branch/master?svg=true
[5]: https://ci.appveyor.com/project/harpocrates/pretty-ghci/branch/master