Forum: Ruby N00b question about Infinity and Float

Announcement (2017-05-07): www.ruby-forum.com is now read-only since I unfortunately do not have the time to support and maintain the forum any more. Please see rubyonrails.org/community and ruby-lang.org/en/community for other Rails- und Ruby-related community platforms.
D7e150e675abb80df7659fe14e7ac0a0?d=identicon&s=25 Kedar Mhaswade (kedarmhaswade)
on 2008-12-31 04:13
Folks,

A new user. Please be kind. I have checked
http://www.ruby-forum.com/topic/74141#new, but could not find what I was
looking for.

See following irb session:

start

irb(main):004:0* google=10**100
=>
10000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000
irb(main):005:0> googleplex=10**google
(irb):5: warning: in a**b, b may be too big
=> Infinity
irb(main):006:0> google.class
=> Bignum
irb(main):007:0> googleplex.class
=> Float

end

This was nice! But, I expected googleplex.class to be BigNum. Is
Infinity a Float?

Why?

Thanks in advance,
Kedar
C06869c119472a139eb163b72040b0db?d=identicon&s=25 Bertram Scharpf (Guest)
on 2008-12-31 05:25
(Received via mailing list)
Hi,

Am Mittwoch, 31. Dez 2008, 12:12:55 +0900 schrieb Kedar Mhaswade:
>
> This was nice! But, I expected googleplex.class to be BigNum. Is
> Infinity a Float?

I like this kind of questions. A weird example, though; I would
prefer an exception. BigNum * BigNum may not result in a Float.
Hit me with your refutations.

Bertram
3bb23e7770680ea44a2d79e6d10daaed?d=identicon&s=25 M. Edward (Ed) Borasky (Guest)
on 2008-12-31 08:23
(Received via mailing list)
Bertram Scharpf wrote:
>> => Bignum
> Bertram
>
>
Hmmm ... "google" is a Bignum (multi-precision integer). "10" is an
Integer. So you are raising an Integer to a Bignum power. So it boils
down to how Ruby raises an Integer to a Bignum power. Now if this were
an "ideal machine", it would perform some kind of exact, and very long
running, exponentiation routine. Clearly it didn't ... it looked at the
numbers and said, "Whoa!" :)

Yeah ... it should have returned an exception, not a Float. But there
are plus and minus Infinity in the IEEE floating point number spec, so I
guess it makes sense to return that. But in theory, given enough memory
for the digits and enough compute time, it could return a Bignum. An
estimate of the amount of memory required is left as an exercise for the
student. :)

Incidentally, the correct spelling is "googol", not to be confused with
the search engine or the Russian author. :)

--
M. Edward (Ed) Borasky, FBG, AB, PTA, PGS, MS, MNLP, NST, ACMC(P), WOM

I've never met a happy clam. In fact, most of them were pretty steamed.
This topic is locked and can not be replied to.