Re: question 2

*To*: mathgroup at smc.vnet.net*Subject*: [mg75854] Re: question 2*From*: Szabolcs <szhorvat at gmail.com>*Date*: Sat, 12 May 2007 03:01:08 -0400 (EDT)*Organization*: University of Bergen*References*: <200705110930.FAA06120@smc.vnet.net> <f21gav$7jv$1@smc.vnet.net>

Chris Chiasson wrote: > Expressions with heads that have the Attribute Orderless are > automatically sorted. In this case, I think the culprit is Plus. > > On 5/11/07, dimitris <dimmechan at yahoo.com> wrote: >> The ordering has to do with the letters? >> That is, >> First "e" then "o" in f1, and "x" first and >> then "y" in f2 rather than with the order >> of 4 and 8? It seems that Plus is treated in a special way, though only Times and Power are mentioned in the documentation. http://documents.wolfram.com/mathematica/book/section-A.3.9 In[1]:= Attributes[f]=Attributes[Plus] Out[1]= {Flat,Listable,NumericFunction,OneIdentity,Orderless,Protected} In[2]:= OrderedQ[{f[2,a],f[1,b]}] Out[2]= False In[3]:= OrderedQ[{Plus[2,a],Plus[1,b]}] Out[3]= True True

**References**:**question 2***From:*dimitris <dimmechan@yahoo.com>