Add ihaskell-graphviz to display graphs.

Requires 'Graphviz' installed.

ihaskell-display/ihaskell-graphviz/IHaskell/Display/Graphviz.hs

+
+-- | A module to help displaying information using the amazing Graphviz
+-- (https://www.graphviz.org/) graph layouts.
+--
+-- You need to install and have graphviz tools available in your environment.
+-- 
+-- Currently only 'dot' is provided as a proof-of-concept.  This module may be
+-- split in two (a package as an helper to Graphviz command line and this
+-- package to provide 'IHaskellDisplay' instances.
+--
+-- Minimal notebook example:
+--
+-- @ :extension OverloadedStrings @
+-- @ import IHaskell.Display.Graphviz @
+-- @ dot LeftToRight "digraph { l -> o; o -> v; v -> e; h -> a ; a -> s; s -> k ; k -> e ; e -> l ; l -> l}" @
+module IHaskell.Display.Graphviz (
+    dot
+  , RankDir(..)
+  , Graphviz
+  ) where
+
+import           Data.ByteString (ByteString)
+import qualified Data.ByteString.Char8 as Char
+import           System.Process (readProcess)
+import           IHaskell.Display
+
+-- | The body of a Graphviz program.
+--
+-- e.g. @ graph { a -- b } @
+type GraphvizProgramBody = ByteString
+
+-- | Plot direction when laying out with Dot.
+data RankDir = LeftToRight | TopToBottom
+  deriving (Show, Eq, Ord)
+
+-- | Main Graphviz object.
+data Graphviz =
+  Dot !RankDir !ByteString
+  -- ^ A Graphviz plotted using Dot (only available currently).
+
+-- | Create a 'Graphviz' using 'dot'.
+dot :: RankDir -> GraphvizProgramBody -> Graphviz
+dot = Dot
+
+instance IHaskellDisplay Graphviz where
+  display fig = do
+    pngDisp <- graphDataPNG fig
+    return $ Display [pngDisp]
+
+rankdirOpt :: RankDir -> String
+rankdirOpt LeftToRight = "-Grankdir=LR"
+rankdirOpt TopToBottom = "-Grankdir=TB"
+
+name = "ihaskell-graphviz."
+
+-- Width and height
+w = 300
+h = 300
+
+graphDataPNG :: Graphviz -> IO DisplayData
+graphDataPNG (Dot rankdir dotBody) = do
+  switchToTmpDir
+
+  let fname = name ++ "png"
+  -- Write the image.
+  ret <- readProcess "dot" ["-Tpng", "-o", fname, rankdirOpt rankdir] (Char.unpack dotBody)
+
+  -- Force strictness on readProcess, read file, and convert to base64.
+  imgData <- seq (length ret) $ Char.readFile fname
+  return $ png w h $ base64 imgData

ihaskell-display/ihaskell-graphviz/LICENSE

+The MIT License (MIT)
+
+Copyright (c) 2013 Lucas DiCioccio
+
+Permission is hereby granted, free of charge, to any person obtaining a copy of
+this software and associated documentation files (the "Software"), to deal in
+the Software without restriction, including without limitation the rights to
+use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of
+the Software, and to permit persons to whom the Software is furnished to do so,
+subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in all
+copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS
+FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR
+COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER
+IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
+CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.

ihaskell-display/ihaskell-graphviz/Setup.hs

+import           Distribution.Simple
+
+main = defaultMain

ihaskell-display/ihaskell-graphviz/ihaskell-graphviz.cabal

+-- The name of the package.
+name:                ihaskell-graphviz
+
+-- The package version.  See the Haskell package versioning policy (PVP)
+-- for standards guiding when and how versions should be incremented.
+-- http://www.haskell.org/haskellwiki/Package_versioning_policy
+-- PVP summary:      +-+------- breaking API changes
+--                   | | +----- non-breaking API additions
+--                   | | | +--- code changes with no API change
+version:             0.1.0.0
+
+-- A short (one-line) description of the package.
+synopsis:            IHaskell display instance for GraphViz (external binary)
+
+-- A longer description of the package.
+-- description:
+
+-- URL for the project homepage or repository.
+homepage:            http://www.github.com/gibiansky/ihaskell
+
+-- The license under which the package is released.
+license:             MIT
+
+-- The file containing the license text.
+license-file:        LICENSE
+
+-- The package author(s).
+author:              Lucas DiCioccio <lucas@dicioccio.fr>
+
+-- An email address to which users can send suggestions, bug reports, and
+-- patches.
+maintainer:          Lucas DiCioccio <lucas@dicioccio.fr>,
+                     Andrew Gibiansky <andrew.gibiansky@gmail.com>
+
+-- A copyright notice.
+-- copyright:
+
+category:            Development
+
+build-type:          Simple
+
+-- Extra files to be distributed with the package, such as examples or a
+-- README.
+-- extra-source-files:
+
+-- Constraint on the version of Cabal needed to build this package.
+cabal-version:       >=1.16
+
+library
+  -- Modules exported by the library.
+  exposed-modules:     IHaskell.Display.Graphviz
+
+  -- Modules included in this library but not exported.
+  -- other-modules:
+
+  -- Other library packages from which modules are imported.
+  build-depends:       base >=4.9 && <5,
+                       bytestring,
+                       process,
+                       ihaskell >= 0.6.2
+
+  -- Directories containing source files.
+  -- hs-source-dirs:
+
+  -- Base language which the package is written in.
+  default-language:    Haskell2010

ihaskell-display/ihaskell-graphviz/stack.yaml

+flags: {}
+packages:
+- '.'
+resolver: lts-9.21
+extra-deps: []

stack.yaml

@@ -10,6 +10,7 @@ packages:
     - ./ihaskell-display/ihaskell-charts
     - ./ihaskell-display/ihaskell-diagrams
     - ./ihaskell-display/ihaskell-gnuplot
+    - ./ihaskell-display/ihaskell-graphviz
     - ./ihaskell-display/ihaskell-hatex
     - ./ihaskell-display/ihaskell-juicypixels
     - ./ihaskell-display/ihaskell-magic