\documentclass{article}

\usepackage{verbatim}
\newenvironment{code}{\verbatim}{\endverbatim}

\begin{document}

\section*{Latex $<$3 Haskell}
Check it out: this file is both valid \LaTeX{}, and valid Haskell!

\begin{code}
main = putStrLn "Check it out: this file is both valid LaTeX, and valid Haskell!"
\end{code}

Compile with
\begin{verbatim}
latex latex-and-haskell.lhs   # for latex
ghc latex-and-haskell.lhs     # for haskell
\end{verbatim}

\end{document}