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. Thanks Steve
