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    <p>Your implementation will not be efficient since the list is not the correct representation to use if you need to change item order, as in a rotation. (Imagine a round-robin scheduler with many thousands of jobs, taking the front job and placing it at the end when done.) </p> <p>So we're actually just asking ourself what would be the way with least overhead to do this on lists anyway. But then what qualifies as overhead that we want to get rid of? One can often save a bit of computation by consing (allocating) more objects, or the other way around. One can also often have a larger than needed live-set during the computation and save allocation that way.</p> <hr> <pre><code>first_last([First|Tail]) -&gt; put_last(First, Tail). put_last(Item, []) -&gt; [Item]; put_last(Item, [H|Tl]) -&gt; [H|put_last(Item,Tl)]. </code></pre> <p>Ignoring corner cases with empty lists and such; The above code would cons the final resulting list directly. Very little garbage allocated. The final list is built as the stack unwinds. The cost is that we need more memory for the entire input list and the list in construction during this operation, but it is a short transient thing. My damage from Java and Lisp makes me reach for optimizing down excess consing, but in Erlang you dont risk that global full GC that kills every dream of real time properties. Anyway, I like the above approach generally.</p> <hr> <pre><code>last_first(List) -&gt; last_first(List, []). last_first([Last], Rev) -&gt; [Last|lists:reverse(Rev)]; last_first([H|Tl], Rev) -&gt; last_first(Tl, [H|Rev]). </code></pre> <p>This approach uses a temporary list called Rev that is disposed of after we have passed it to lists:reverse/1 (it calls the BIF lists:reverse/2, but it is not doing anything interesting). By creating this temporary reversed list, we avoid having to traverse the list two times. Once for building a list containing everything but the last item, and one more time to get the last item.</p>
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    1. POright rotate a List in Erlang
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    1. COThis approach is nice and clean indeed, but cannot be generalized to rotate N elements (as in the question). Of course you can apply these functions N times, but then you are off the efficiency charts.
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    2. COYes. I failed to notice he wanted a rotation count.
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