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Re: [Axiom-developer] Counting Elements in Cyclic List


From: root
Subject: Re: [Axiom-developer] Counting Elements in Cyclic List
Date: Mon, 1 Sep 2008 16:27:18 -0400

>I'm new to axiom and tried to count the elements in a cyclic list and
>expected to get %PositiveInfiniy as Answer. Instead it resulted in an
>infinite loop. Version is Axiom 3.9 (September 2005)
>
>=======================================
>What I've did:
>
>u:= [9,2,4,7]; concat! (u, [1,2,42]); end := rest(u,4); part :=
>rest(u,2);  setrest!(end, part);
>
>u is now [9,2,(42,7,1)] -- the () are the cyclic part
>
>when you count the elements using "#u" then it resolves in a loop.
>
>=======================================
>What I 've expected:
>
>There should be a Property like "isCyclic?" that tests if the list is
>cyclic. The new code for counting should be something like
>
>count(x) == if isCyclic? x then return ?PositiveInfinity else #x
>
>=======================================
>Question:
>Is this fixed already in a newer version?

In the documentation it states:
  "Note that using the "#" operator on a list with cycles
   causes Axiom to enter an infinte loop"

See:
<http://axiom-developer.org/axiom-website/documentation.html>
in Volume 0: Axiom Jenks and Sutor p41

Tim




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