Start Wildcard elimination example

unify.tex

@@ -108,6 +108,22 @@ List<? extends Object> someList(){
 }
 \end{lstlisting}
 
+\subsection{Wildcard Elimination Example}
+\begin{lstlisting}
+  <X> List<X> concat(List<X> l, List<X> l2){ ... }
+  someList(){
+    return new List("String") :? new List(42);
+  }
+
+  concat(someList(), someList());
+\end{lstlisting}
+
+Let's add an additional method call to the previous example.
+The \texttt{concat} method takes two lists of the same generic type.
+\texttt{concat} cannot be invoked with two existential lists.
+%TODO: Explain capture conversion
+
+
 \subsection{Description}
 The \unify{} algorithm tries to find a solution for a set of constraints like
 $\set{\exptype{List}{String} \lessdot \tv{a}, \exptype{List}{Integer} \lessdot \tv{a}}$.