Re: Sort with -Infinity fails

*To*: mathgroup at smc.vnet.net*Subject*: [mg73870] Re: [mg73822] Sort with -Infinity fails*From*: János <janos.lobb at yale.edu>*Date*: Fri, 2 Mar 2007 06:36:20 -0500 (EST)*References*: <200703011117.GAA28248@smc.vnet.net>

On Mar 1, 2007, at 6:17 AM, Tom Aldenberg wrote: > Dear MathGroup, > > Minus Infinity (-Infinity) is smaller than -8, but Sort does not > sort it as > expected. > Is there a Real minus Infinity? > > > In[75]:= > -Infinity < -8 > Out[75]= > True > > In[76]:= > Sort[{-Infinity, -8, 5}] > Out[76]= > {-8, 5, -=B0} > > > Regards, > > Tom Aldenberg > > ______________________________________________________________________= > ______ > > DISCLAIMER: http://www.rivm.nl/disclaimer.htm > Well, being a newbie I looked up sort in the Help. I found that Sort follows the "canonical Order" - whatever that is. Appendix says: "Integers, rational and approximate real numbers are ordered by their = numerical values" "Symbols are ordered according to their names, and in the event of a tie, by their contexts" Lets have the following list: In[50]:= lst = {Infinity, -Infinity, -8, 5} In[54]:= Head /@ lst Out[54]= {DirectedInfinity, DirectedInfinity, Integer, Integer} So, if you want to have the "normal" result you have to use a different ordering in Sort to force a numerical value on DirectedInfinity. In[53]:= Sort[lst, Less] Out[53]= {-Infinity, -8, 5, Infinity} J=87nos ======================== "I think I may need a bathroom break? Is this possible?" --G.W.Bush http://news.bbc.co.uk/2/hi/americas/4249646.stm

**References**:**Sort with -Infinity fails***From:*Tom Aldenberg <Tom.Aldenberg@rivm.nl>