Re: Re: Re: Bug Report - Two numerical values for a same variable

*To*: mathgroup at smc.vnet.net*Subject*: [mg54353] Re: [mg54322] Re: Re: Bug Report - Two numerical values for a same variable*From*: Murray Eisenberg <murray at math.umass.edu>*Date*: Sat, 19 Feb 2005 02:31:54 -0500 (EST)*Organization*: Mathematics & Statistics, Univ. of Mass./Amherst*References*: <00ed01c512b0$2f242850$6400a8c0@Main> <curpbn$r28$1@smc.vnet.net> <200502150438.XAA29728@smc.vnet.net> <cv0953$jbg$1@smc.vnet.net> <200502171530.KAA02364@smc.vnet.net>*Reply-to*: murray at math.umass.edu*Sender*: owner-wri-mathgroup at wolfram.com

Right. And one can use something like StringTake["HelloWorld", {6}] to extract part of the "atom" that is the string there. (This is in contrast, say, to taking Floor[3.14] which is clearly applying an "operation" to the atome 3.14.) So that's why I originally said I wasn't too sure why strings were atoms, either. Steve Luttrell wrote: > I am also uneasy about Complex and Rational being atomic. The only reason I > can think of is that computational efficiency might prefer these to be > atomic objects. > > You can do the following to extract the parts of a Rational: > > Numerator[Rational[1, 2]] > > Denominator[Rational[1, 2]] > > Analogously, Re and Im can be used to extract the "parts" of a Complex. > > Steve Luttrell > > "Murray Eisenberg" <murray at math.umass.edu> wrote in message > news:cv0953$jbg$1 at smc.vnet.net... > >>The manipulations below are precisely what's so confusing about Rational >>objects (and Complex objects) being atoms. If >> >> 1/2 /. Rational[x_, 2] -> Rational[x, 7] >> >>works, then why not the following? >> >> Part[Rational[1, 2], 2] >> >>I can "believe" that integers and reals (and maybe strings) are atoms; >>but believing that rationals and complex numbers are atoms is a hard >>thing to swallow! >> >>This has always bothered me -- and hence given me trouble trying to, um, >>rationalize this to students when I've taught Mathematica. >> >> >>Scott Hemphill wrote: >> >>>DrBob <drbob at bigfoot.com> writes: >>> >>> >>> >>>>That explains it, but only in the sense that "things fall down" is a >>>>theory of gravity. Why should Rationals be atomic, for goodness sake? And >>>>how did I use Mathematica all this time without hearing about it? >>>> >>>>Sigh... >>> >>> >>> >>>In[1]:= FullForm[1/2] >>> >>>Out[1]//FullForm= Rational[1, 2] >>> >>>In[2]:= 1/2 /. Rational[x_,2] -> Rational[x,7] >>> >>> 1 >>>Out[2]= - >>> 7 >>> >>>Scott >> >>-- >>Murray Eisenberg murray at math.umass.edu >>Mathematics & Statistics Dept. >>Lederle Graduate Research Tower phone 413 549-1020 (H) >>University of Massachusetts 413 545-2859 (W) >>710 North Pleasant Street fax 413 545-1801 >>Amherst, MA 01003-9305 >> > > > > -- Murray Eisenberg murray at math.umass.edu Mathematics & Statistics Dept. Lederle Graduate Research Tower phone 413 549-1020 (H) University of Massachusetts 413 545-2859 (W) 710 North Pleasant Street fax 413 545-1801 Amherst, MA 01003-9305

**Follow-Ups**:**Re: Re: Re: Re: Bug Report - Two numerical values for a same variable***From:*Andrzej Kozlowski <akoz@mimuw.edu.pl>

**References**:**Re: Bug Report - Two numerical values for a same variable***From:*Scott Hemphill <hemphill@hemphills.net>

**Re: Re: Bug Report - Two numerical values for a same variable***From:*"Steve Luttrell" <steve_usenet@_removemefirst_luttrell.org.uk>