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+\section{Conclusion}
+\label{sec:concl}
+
+Walking through the implementation of a While interpreter we have seen
+different advantages of doing this in a functional style.
+
+First of all, the syntax could be translated directly from grammar to type
+definitions. It is true that simple algebraic data types, as used in
+\autoref{sec:ast}, could be simulated with enumeration types and pointers in
+an imperative style. However, any one will agree that the functional
+definitions are better readable, making their usage less error-prone.
+
+Secondly, in \autoref{sec:eval} we saw that functional programming languages
+allow us to easily work with higher order functions: we did not need to
+implement the state as a lookup table but could simply use a function.
+
+We then discussed the use of the \CI{Either} monad for error reporting. Monadic
+binding lets us work easily with calculations that may fail. Moreover, in
+\autoref{sec:interp} we saw that monads also let us specify execution order.
+
+In general, we have seen that a functional style allows us to stay close to the
+semantic definitions of a language. This makes it very easy to verify that our
+implementation of the semantics is correct. Proofs that hold for the semantics
+(like completeness or correctness with respect to axiomatic semantics) easily
+apply to the interpreter as well, once the correctness of the interpreter has
+been established --- this is generally a trivial task. Furthermore, the final
+implementation is better readable and thus easier to maintain.