\documentclass{article}
\usepackage{tikz}
\usepackage[utf8]{inputenc}
\author{Daniel Díaz}
\title{Embedding HaTeX in \emph{haskintex}}
\begin{document}
\maketitle
Below is the \emph{Spira Mirabilis} inserted using the HaTeX
package.
\begin{writehaskell}
import Text.LaTeX
import Text.LaTeX.Packages.TikZ.Simple

spiral :: Figure
spiral = LineWidth (Pt 2) $
    pathImage 0.01 (0,4) $
      \t -> ( a * exp t * cos (b*t)
            , a * exp t * sin (b*t)
              )
  where
    a = 0.1 ; b = 4
\end{writehaskell}
\hatex{center $ tikzpicture $ figuretikz spiral}
\end{document}