On 03/04/2010 03:53 PM, Steve Teale wrote: > On Wed, 2010-03-03 at 16:52 -0500, John S. Fine wrote: >> Part of your confusion is over the difference between "precision" and >> "accuracy". >> >> A floating point format has a FINITE number of specific values that can >> be stored with infinite accuracy. You happen to have chosen values that >> are in that finite set. >> >> You can set the precision of your output to whatever (finite value) you >> like. It may be much more than the accuracy of your number. It may be >> much less than the accuracy of your number (especially if the accuracy >> of your number is infinite). >> >> Even if the accuracy of a stored floating point number is infinite, it >> may be possible for the algorithm that converts it from binary to >> decimal to introduce some inaccuracy. I'm not sure of those details. >> Your results seem to indicate that translation is done surprisingly well. >> >> To help you understand, instead of outputting just d each time, output >> both d and d+1. At some point d will still be 100% accurate but d+1 >> will not be accurate, in fact it will be exactly equal to d. > > John, > > Congratulations on a helpful answer. Yours was the first one that did > not display the almost conventional GCC guru arrogance. > > GCC would have a lot more participants/helpers if it were not for this > unwritten convention of rudeness in the community. > > To be fair, this isn't just a GCC thing. I've worked in various shops > where the software paid the wages, but if a new employee asked for help > he/she would get a similar response. > > I understand the impatience of the gurus. If they tried to answer every > naive question they'd never get any work done > > But, if you don't have anything helpful to say, then maybe it's better > to bite your tongue! The person you are responding to may be an idiot, > but he/she is not the only recipient of your message. I strongly disagree. The main problem may have been that the OP didn't understand floating-point arithmetic, so the advice to find out about that was appropriate. Let's see what the OP says. Andrew.
