Re: Sort problem

*To*: mathgroup at smc.vnet.net*Subject*: [mg81719] Re: [mg81678] Sort problem*From*: DrMajorBob <drmajorbob at bigfoot.com>*Date*: Tue, 2 Oct 2007 05:36:40 -0400 (EDT)*References*: <29806953.1191260945481.JavaMail.root@m35>*Reply-to*: drmajorbob at bigfoot.com

The default Sort criterion is OrderedQ[{#1,#2}]& (canonical ordering) and that's quite different from #1 < #2 & (Less). r < a is neither True nor False (unless r and a are numbers), so in your example it doesn't cause elements to be switched in the sort process. Here are a couple of ways to get what you seem to want: Sort[{{r, 2}, {a, 3}, {x, 4}}, OrderedQ[First /@ {##}] &] {{a, 3}, {r, 2}, {x, 4}} SortBy[{{r, 2}, {a, 3}, {x, 4}}, First] {{a, 3}, {r, 2}, {x, 4}} Bobby On Mon, 01 Oct 2007 03:49:55 -0500, Donald DuBois <donabc at comcast.net> wrote: > Hello, > > This Sort works > > In[32]:= Sort[{r, a, x}] > > Out[32]= {a, r, x} > > but this one doesn't: > > In[33]:= Sort[{{r, 2}, {a, 3}, {x, 4}}, #1[[1]] < #2[[1]] &] > > Out[33]= {{r, 2}, {a, 3}, {x, 4}} > > > What am I doing wrong? > > Don > > -- DrMajorBob at bigfoot.com