On Mon, Feb 28, 2005 at 07:55:36PM -0600, Eric Wilhelm wrote: > I like the one where you get the mathematically-correct (or at least > mathematically-useful) infinity. > > $perl -le 'use bigint; $x = 1/0; print $x+1' > inf > > $perl -le 'use bigint; $x = 1/0; print 1/$x' > 0
and what should these print? $perl -le 'use bigint; $x = 2/0; print $x*0' $perl -le 'use bigint; $x = 1/0; print ($x+1)-$x' $perl -le 'use bigint; $x = 1/0; print ($x*2)/$x' Allowing inf might make some sense in an interactive calculator but it's a bad idea in a programming langague. For example there's no way to evaluate $x/$y when both are inf or even $x * 0 when $x is inf. Perl would have to die with an Inf error. It's bad enough trying to find the real source of a divide by zero error but for an Inf error you might have to find 2 occurrences of divide by zero, figure out which one is wrong and then go fix a divide by zero error. It's also possible that neither of them is wrong and that both infs are supposed to be there in which you have a big refactoring job ahead. There is actually a system of arithmetic which allows infinitely large and small values (it provides an infinite number of infinitely large/small numbers) and produces "sensible" results for any expression, no matter if the values involved are finite or inifintely large/small. In this system (x * 2) / x is always 2 for any x, except x = 0 - even in this system division by zero is not allowed. http://mathforum.org/dr.math/faq/analysis_hyperreals.html has a good explanation. F
