<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN"> <HTML><HEAD> <META http-equiv=Content-Type content="text/html; charset=iso-8859-1"> <META content="MSHTML 6.00.6000.16414" name=GENERATOR> <STYLE></STYLE> </HEAD> <BODY bgColor=#ffffff> <DIV>Hi Eli,</DIV> <DIV>I am interested in how you solved the problem using a vector while not knowing beforehand the maximum number that will be generated while cycling.</DIV> <DIV>Jos koot</DIV> <DIV> </DIV> <DIV>(((((lambda(x)((((((((x x)x)x)x)x)x)x)x))<BR>    (lambda(x)(lambda(y)(x(x y)))))<BR>   (lambda(x)(x)x))<BR>  (lambda()(printf "Greetings, Jos~n"))))</DIV> <BLOCKQUOTE style="PADDING-RIGHT: 0px; PADDING-LEFT: 5px; MARGIN-LEFT: 5px; BORDER-LEFT: #000000 2px solid; MARGIN-RIGHT: 0px"> <DIV style="FONT: 10pt arial">----- Original Message ----- </DIV> <DIV style="BACKGROUND: #e4e4e4; FONT: 10pt arial; font-color: black"><B>From:</B> <A title=eli@barzilay.org href="mailto:eli@barzilay.org">Eli Barzilay</A> </DIV> <DIV style="FONT: 10pt arial"><B>To:</B> <A title=dyoo@cs.wpi.edu href="mailto:dyoo@cs.wpi.edu">Daniel Yoo</A> </DIV> <DIV style="FONT: 10pt arial"><B>Cc:</B> <A title=plt-scheme@list.cs.brown.edu href="mailto:plt-scheme@list.cs.brown.edu">plt-scheme@list.cs.brown.edu</A> </DIV> <DIV style="FONT: 10pt arial"><B>Sent:</B> Saturday, March 17, 2007 9:34 PM</DIV> <DIV style="FONT: 10pt arial"><B>Subject:</B> Re: [plt-scheme] Effect of caching using hash-tables vs vectors</DIV> <DIV><BR></DIV>On Mar 17, Daniel Yoo wrote:<BR>> Just for fun, I did a solution for the 3n+1 problem from Programming <BR>> Challenges:<BR>> <BR>>      <A href="http://acm.uva.es/p/v1/100.html">http://acm.uva.es/p/v1/100.html</A><BR>> [...]<BR><BR>Unrelated to your post -- but I played with this a while ago.  I<BR>eventually realized that there are certain bit patterns that need to<BR>be checked in a specific way, and ended up writing Scheme code that<BR>would generate C code for each of these tests, then run it.  I managed<BR>to prove that the thing converges up to something in the neighborhood<BR>of numbers that are known to converge.  (I think it was something<BR>around 1e20.)  I can send you the file if you're interested -- but it<BR>will take some time to decipher what it's doing.<BR>-- <BR>          ((lambda (x) (x x)) (lambda (x) (x x)))          Eli Barzilay:<BR>                  <A href="http://www.barzilay.org/">http://www.barzilay.org/</A>                 Maze is Life!<BR>_________________________________________________<BR>  For list-related administrative tasks:<BR>  <A href="http://list.cs.brown.edu/mailman/listinfo/plt-scheme">http://list.cs.brown.edu/mailman/listinfo/plt-scheme</A><BR></BLOCKQUOTE></BODY></HTML>