And if that isn&#39;t a possibility, you can use pattern matching:<br><br>bla (x:y:z:[]) = do something<br>bla _ = do nothing<br><br><br><div class="gmail_quote">On Tue, Sep 28, 2010 at 4:41 PM, Ozgur Akgun <span dir="ltr">&lt;<a href="mailto:ozgurakgun@gmail.com">ozgurakgun@gmail.com</a>&gt;</span> wrote:<br>

<blockquote class="gmail_quote" style="margin: 0pt 0pt 0pt 0.8ex; border-left: 1px solid rgb(204, 204, 204); padding-left: 1ex;">Hi,<div class="im"><br><br><div class="gmail_quote">On 28 September 2010 15:07, Martin Tomko <span dir="ltr">&lt;<a href="mailto:martin.tomko@geo.uzh.ch" target="_blank">martin.tomko@geo.uzh.ch</a>&gt;</span> wrote:<br>

<blockquote class="gmail_quote" style="margin: 0pt 0pt 0pt 0.8ex; border-left: 1px solid rgb(204, 204, 204); padding-left: 1ex;">
I want to have a function that acts only on lists of length 3 (I have a function that filters a list of lists and returns only those of that length). I guess I could change them into tuples (is there a way?)</blockquote>

</div>
<div><br></div></div><div>Well if both the producer and the consumer of this value are your own functions, you can use something other than a list. You can also implement a length indexed list, or use such an implementation but it will be overkill for this task, I think.</div>


<div><br></div><div>The two options are either implementing a wrapper type with three fields, or using a 3-tuple.</div><div>I would use a 3-tuple in both the producer and consumer functions.</div><div><br></div><div>Best,</div>


<div>Ozgur</div>
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