Zora.TreeGraphing

A typeclass with default implementation for graphing trees with Haskell GraphViz.

Documentation

class Zoldable g => Graphable g where

A typeclass for algebraic data types that are able to be graphed. For these descriptions, assume the following example data type:

 data Tree a = Empty | Leaf a | Node a (Tree a) (Tree a)

See the supporting file dot.hs for an example of how to graph your data type.

Methods

value :: g a -> a

Gets the value contained in a node. For example,

 value (Empty) = error "Empty nodes don't contain values."
 value (Leaf x) = x
 value (Node x _ _) = x

get_children :: g a -> [g a]

Gets the children of the current node. For example,

 get_children (Empty) = error "Empty nodes don't have children."
 get_children (Leaf _) = []
 get_children (Node _ l r) = [l, r]

is_empty :: g a -> Bool

Returns whether a node is empty. Sometimes, when declaring algebraic data types, it is desirable to have an Empty value constructor. If your data type does not have an Empty value constructor, just always return False.

 is_empty (Empty) = True
 is_empty _ = False

graph :: forall a. (Show a, Ord a) => g a -> Graph

Returns a Graph for the given Graphable type. You shouldn't need to override this implementation.