doc-src/TutorialI/fp.tex

 information is stored only in the final node associated with the string, many
 nodes do not carry any value. This distinction is modeled with the help
 of the predefined datatype \isa{option} (see {\S}\ref{sec:option}).
 \input{Trie/document/Trie.tex}
 
-\begin{exercise}
-  Write an improved version of \isa{update} that does not suffer from the
-  space leak in the version above. Prove the main theorem for your improved
-  \isa{update}.
-\end{exercise}
-
-\begin{exercise}
-  Write a function to \emph{delete} entries from a trie. An easy solution is
-  a clever modification of \isa{update} which allows both insertion and
-  deletion with a single function.  Prove (a modified version of) the main
-  theorem above. Optimize you function such that it shrinks tries after
-  deletion, if possible.
-\end{exercise}
-
 \section{Total Recursive Functions}
 \label{sec:recdef}
 \index{*recdef|(}
 
 Although many total functions have a natural primitive recursive definition,