Tim Conrow wrote: > Damian Conway said: > > > > print "Inflation rate: " and $inflation = +<> > > > > until $inflation != NaN; > > > > > > This requires that C<NaN != NaN> be false, causing the loop to > > > continue until a valid numeric string is entered. > > > Err. Are you *sure*? That's an C<until>, not a C<while>, you realize? > > Yes. I had to use all my fingers and toes to keep everything straight, > but I think I did. :-) In the semantics you show (different from IEEE > semantics) "NaN==NaN" is true, so "NaN!=NaN" is false, which is why the > loop continues until a valid number is entered.
Hi, This is my first post here, so don't laugh if I say something stupid. :) I haven't got any contact with NaN before, but when Tim pointed that NaN!=NaN is true in IEEE I thought that it does make sense. I see pros and cons and it's not so ugly and non-intuitive as it can look. When comparing $a and $b as numbers there is no need for $a==$b!=NaN, if NaN!=NaN then $a==$b is ok for any values of $a and $b, it would be true only if $a and $b are numbers and they are equal. If NaN==NaN is true, then the longer $a==$b!=NaN is needed. So when comparing two scalars as numbers NaN!=NaN being true makes it easier. But then "until $inflation != NaN" would be useless as NaN!=anything is always true (NaN!=NaN, and NaN!=anynumber). With NaN!=NaN some other way like $x.isNaN or $x.isnum would be needed. Or maybe NaN evaluates to 'NaN' in string context and +$x eq 'NaN' (or +$x eq NaN) could be used? NaN==NaN being false is in fact very intuitive for me, as NaN is something without any numerical meaning, so numerically compared to anything doesn't make sense (as == means numerical equality, not just equality). Maybe it should be undef instead of false? So OK, tell me if I get it right, and how (and why) it will look in Perl 6. From Exegesis I see that NaN==NaN, but that's not stated in Apocalypse (or I just missed it). BTW, I really like the direction of Perl 6 development, all of you are doing really great job here. I was very surprised when I saw the negative feedback on Slashdot, and I thought that if my enthusiasm is so abnormal, than maybe it's a sign that I should join your team. :) Really, I'd love to help with Perl 6 development if I can be useful somehow. - RaFaL Pocztarski, [EMAIL PROTECTED]
