Re^5: IF condition with a range (updated)

Frankly with Inf, it's probably a good thing if your code doesn't treat two infinite values as being equal

That's a rather novel approach to overflow, and one that I would discourage.

Similarly, wrt to underflow, one could then say:

Frankly with 0, it's probably a good thing if your code doesn't treat two zero values as being equal.

my $x = 1e-5000; # 0
my $y = 1e-5100; # 0

print "equal\n" if $x==$y; # says "equal" even though mathematically they are not

That's also an approach that I would discourage.

Cheers,
Rob

Comment on Re^5: IF condition with a range (updated)

Replies are listed 'Best First'.
Re^6: IF condition with a range (updated) by tobyink (Canon) on Jul 17, 2018 at 11:38 UTC
Well, the difference between 1e-5000 and 1e-5100 is pretty small. For most intents and purposes, there is no difference. The difference between 666 and 777 is a lot bigger. By my calculations, the latter is 659669 orders of magnitude bigger than the former. (That is, to approximate 777, you'd need to add 659669 zeroes to the end of 666.) toby döt ink	[reply]
Re^7: IF condition with a range (updated) by syphilis (Archbishop) on Jul 17, 2018 at 13:25 UTC
Well, the difference between 1e-5000 and 1e-5100 is pretty small. For most intents and purposes, there is no difference Heh ... I thought this was about "mathematical equality", but suddenly it's now also about "intents and purposes". For double precision NVs I could have chosen much larger values of (say) 1e-324 and 1e-325 ... but you're probably not going to be swayed by that, anyway ;-) By my calculations, the latter is 659669 orders of magnitude bigger than the former Yep, I get the same: `C:\>perl -MMath::MPFR -le "$x=Math::MPFR->new(6 6); print 6 $x; 2.6591197721532269e36305 C:\>perl -MMath::MPFR -le "$x=Math::MPFR->new(7 7); print 7 $x; 3.7598235267837884e695974` [download] Cheers, Rob	[reply] [d/l]