\begin{abstract}
	As the tools provided by programming languages become more abstract and
	semantically complex, it becomes necessary to have systems that can reason
	about these programming languages on a high abstraction level. Functional
	languages can aid interpreter and compiler designers: abstraction is trivial,
	and the close link with mathematics makes it easy to prove properties about
	programs. By means of a case study, an interpreter of the language
	While~\citep{proganal}, the advantages of a functional language for
	imperative code interpretation are shown.
\end{abstract}