Adding an element to a set: `addelt'

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Adding an element to a set: `addelt'

This abstraction adds an element to a list if the element is not yet contained in the list thus preserving the essential characteristic of sets.

$\begin{lstlisting}[language=Scm]{} (define addelt (lambda(x s) (if (memberp x s) s (cons x s)))) \end{lstlisting}$

$\begin{lstlisting}[language=Scm]{} (define l1 (cons one (cons two (cons three ... ...l1)) ;; effective because not yet a member --> 5 1 2 3 4 ; \end{lstlisting}$

Georg P. Loczewski 2004-03-05