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Retrieving the n-th element from a list: `nth'
A list can be used like an array in other programming languages
by using the abstraction `nth' which extracts an element from
a list by using an index pointing to its position.
![\begin{lstlisting}[language=Scm]{}
(define nth
(lambda (n l)
(if (equaln n one)
(car l)
(nth (sub n one) (cdr l)))))
\end{lstlisting}](img101.gif)
![\begin{lstlisting}[language=Scm]{}
(define l1 (cons one (cons three (cons four nil))))
;
(ldisp! (nth two l1))
--> 3
\end{lstlisting}](img102.gif)
Georg P. Loczewski
2004-03-05