From b87fa9a0489ec25a07b52bd98c3b265e06903ebb Mon Sep 17 00:00:00 2001
From: JanUlrich <andi@michlaustderaffe.de>
Date: Wed, 14 Feb 2024 15:44:46 +0100
Subject: [PATCH] intro comment

---
 introduction.tex | 27 +++++++++++++++++++++++++++
 1 file changed, 27 insertions(+)

diff --git a/introduction.tex b/introduction.tex
index cf39cc1..40ce1d5 100644
--- a/introduction.tex
+++ b/introduction.tex
@@ -172,6 +172,33 @@ m(l) {
 
 $\tv{l} \lessdotCC \exptype{List}{\wtv{x}}, \tv{l} \lessdotCC \wtv{x}$
 
+% One possible solution:
+% \begin{verbatim}
+% List<Object> m(List<Object> l) {
+%     return l.add(l);
+% }
+% \end{verbatim}
+
+% No capture conversion for methods in the same class:
+% \begin{verbatim}
+% m() = new List<String>() :? new List<Integer>();
+% id(a) = a
+
+% id(m())
+% \end{verbatim}
+% id will get type List<?> -> List<?>
+% % explain polymorphic recursion here
+% % no capture conversion needed
+
+% The id method is pre typed:
+% \begin{verbatim}
+% <A> List<A> id(List<A> a) = a
+
+% m() = new List<String>() :? new List<Integer>() :? id(m());
+% \end{verbatim}
+% constraint m :: p -> r
+% % Wildcards are only deleted in unify, never generated.
+
 \subsection{Java Wildcards}
 Wildcards are expressed by a \texttt{?} in Java and can be used as parameter types.
 Wildcards can be formalized as existential types \cite{WildFJ}.