Re: should Positive[ complexNumber ] return undefined instead of False?

*To*: mathgroup at smc.vnet.net*Subject*: [mg112626] Re: should Positive[ complexNumber ] return undefined instead of False?*From*: Simon <simonjtyler at gmail.com>*Date*: Thu, 23 Sep 2010 04:23:23 -0400 (EDT)*References*: <i79ht0$og9$1@smc.vnet.net>

3*I is unmutable. It will always be a non-positive number. It is also non-negative and not zero, so it's perfectly reasonable that In[1]:= {Positive@#,Negative@#,PossibleZeroQ@#}&[3I] Out[1]= {False,False,False} Simon On Sep 21, 4:04 pm, "Nasser M. Abbasi" <n... at 12000.org> wrote: > math experts: > > x = 3*I; > Positive[x] > > Out[59]= False > > Should this be undefined or unevaluated? > > If it is False, when there must be an case when it is True, right? but > there is not such case, positive and negative are not defined on the > complex numbers, or Am I missing something? > > I know the above works as documented: > > "Positive[x] gives False if x is manifestly a negative numerical > quantity, a complex numerical quantity, or zero. Otherwise, it remains > unevaluated" > > So, my question is just wanting to know why when Mathematica was > designed, the complexes were not added to the case where they remains > unevaluated in this case? > > --Nasser