Diagrams - Naive fibonacci call tree

The tree of function calls made by a naive Fibonacci implementation.

Author: Brent Yorgey

import Diagrams.Backend.SVG.CmdLine

{-# LANGUAGE NoMonomorphismRestriction #-}

import Diagrams.Prelude

We make use of a tree layout module from the diagrams-contrib package:

import Diagrams.TwoD.Layout.Tree

Generate the tree of naive Fibonacci calls.

fibCalls :: Integer -> BTree Integer
fibCalls 0 = leaf 0
fibCalls 1 = leaf 1
fibCalls n = BNode n (fibCalls (n-1)) (fibCalls (n-2))

Lay out the tree and render it by providing a function to render nodes and a function to render edges.

Just t = uniqueXLayout 2 2 (fibCalls 5)

example = pad 1.1 . centerXY
        $ renderTree
            (\n -> (text ("fib " ++ show n)
                    <> roundedRect 3 1.3 0.3 # fc gold)
            )
            (~~) t
        `atop` square 1 # scaleY 12 # translateY (-5)
                        # scaleX 34
                        # lw none # fc whitesmoke

main = mainWith (example :: Diagram B)