g-regex / WillowTikZ

WillowTikZ

This simple Haskell program illustrates the use of a functorial parser to generate TikZ pictures of willows (trees with respectively a labeled $\scriptstyle\ominus$ and $\scriptstyle\oplus$ node on the leftmost and rightmost branch) from an input string containing square brackets.

Instructions

Clone the repository. To generate the source code for the TikZ picture corresponding to the example string [1]+[2]=[3] run:

runhaskell Main.hs "[1]+[2]=[3]"

After compiling the generated LaTeX code, you get the following:

The generated picture can also be used within other documents. Simply copy the file willow.sty to the directory of your LaTeX project. Then you can use the TikZ picture as follows:

\documentclass{article}
\usepackage{standalone}
\usepackage{willow}
\begin{document}
Here is an example figure:
\begin{figure}[ht]
	\centering
	\input{generated-willow.tex}
	\caption{An example willow.}
\end{figure}
\end{document}

Only alpha-numeric characters and any of '+', '-', '=', '.', ',', ';', ' ', '[', ']' are accepted in the input string. Labels which are longer than 10 characters are truncated.

Compiling

The file Willows.hs has been extracted from the Coq code willows.v. To extract it yourself, run:

coqc willows.v

To compile the Haskell code to an executable, run:

ghc Main.hs