Re: odd mathematica blindspot

*To*: mathgroup at smc.vnet.net*Subject*: [mg56569] Re: odd mathematica blindspot*From*: Peter Pein <petsie at arcor.de>*Date*: Fri, 29 Apr 2005 03:20:30 -0400 (EDT)*References*: <d4klbs$eg7$1@smc.vnet.net> <200504270153.VAA01785@smc.vnet.net> <d4q28r$ol9$1@smc.vnet.net>*Sender*: owner-wri-mathgroup at wolfram.com

Edward Peschko wrote: > From: Edward Peschko <esp5 at pge.com> To: mathgroup at smc.vnet.net > Subject: [mg56569] Re: Re: odd mathematica blindspot > Reply-To: > > On Tue, Apr 26, 2005 at 09:53:49PM -0400, Skirmantas wrote: > >>Hi Ed, >> >>By definition, 9999999999999/10000000000000 is an exact rational number, whereas 0.5 is an approximate real number: > > > Well, that's completely unintuitive.. I understand it, but it still rubs me the > wrong way for some reason. '.5' on paper means that to me - .5 - not .4999999999 > or .50000000001 or whatever internal representation the computer chooses.. In fact, > that's why I got Mathematica in the first place, to get away from this approximate > stuff. So, why do you use it any more?? Take 1/2 in place of 0.5 and be happy. > > Why couldn't mathematica treat .5 as a string, make the internal calculation > and turn .5 into 5/10? Or, barring that, is there a conversion function for this > (going back and forth between rational and approximate real? > In[1]:= Rationalize[0.5] Out[1]= 1/2 see the Mathematica book, chapter 3.2.2. (it should be on your hard disk, accessible by the help browser) > Ed > -- Peter Pein Berlin

**References**:**Re: odd mathematica blindspot***From:*Skirmantas <skirmantas.janusonis@yale.edu>