context-free-art: Generate art from context-free grammars

Create art via context free grammar production rules.

Context free grammar primer

Context free grammars consist of a set of terminal symbols, a set of non-terminal symbols, and production rules that map non-terminals to other symbols.

With a context-free grammar, we can generate strings of terminals that conform to the specified language.

Our language will describe graphics.

Example

import Art.ContextFree.Probabilistic
import Data.List.NonEmpty

-- let's define a Production rule
a = Circle 1

-- this will produce an IO (Maybe Svg) from the blaze-svg package
-- to turn it into a string we can use one of the `blaze-svg` renderers
graphic1 = render $ Circle 1

-- let's create a non-terminal, 'a', which renders a terminal, 'Circle 1'
-- and has an 85% chance of rendering itself, placed to its right
a = NonTerminal $ (100, Circle 1) :| [(85, b)]
b = Mod [Move (2, 0)] a

import Art.ContextFree.Definite
import Data.List.NonEmpty

move = Mod [Move (0, -1.8), Scale 0.8]

armN :: Int -> Symbol
armN 0 = move $ Circle 1
armN n = move $ NonTerminal $
  Circle 1 :| [Mod [Rotate 10] $ armN (n - 1)]

arm :: Symbol
arm = armN 20

spiral = NonTerminal $
  Circle 1 :| [arm, Mod [Rotate 120] arm, Mod [Rotate 240] arm]

The latter produces this graphic:

• Art
  • ContextFree
    • Art.ContextFree.Definite
    • Art.ContextFree.Probabilistic