Diagrams 0.2 release

After meaning to get around to it for quite a while, I’ve finally released version 0.2 of the Haskell diagrams library. Here’s the release announcement. And here’s one of my favorite examples showing off the new path support:

[caption id=“attachment_120” align=“aligncenter” width=“300” caption=“Heighway dragon”][/caption]

I made this Heighway dragon curve in just a few minutes of hacking this afternoon, with the following code:

{- Heighway dragon.  See http://en.wikipedia.org/wiki/Dragon_curve. -}
module Main where

import Graphics.Rendering.Diagrams
import Control.Monad.State
import Data.Maybe

dragonStr :: Int -> String
dragonStr 0 = "FX"
dragonStr n = concatMap rules $ dragonStr (n-1)
  where rules 'X' = "X+YF+"
        rules 'Y' = "-FX-Y"
        rules c = [c]

strToPath :: String -> Path
strToPath s = pathFromVectors . catMaybes $ evalState c (0,-1)
  where c        = mapM exec s
        exec 'F' = Just `fmap` get
        exec '-' = modify left >> return Nothing
        exec '+' = modify right >> return Nothing
        exec _   = return Nothing
        left (x,y)  = (-y,x)
        right (x,y) = (y,-x)

dragon :: Int -> Diagram
dragon = lc red . curved 0.8 . strToPath . dragonStr

main = renderAs PNG "dragon.png" (Width 300) (dragon 12)

A special thank you to Dougal Stanton for adding text rendering support and other features, switching diagrams over to Russell O’Connor’s colour library, and generally helping out with this release.