[ruby-core:30735] [Bug #3429] Integer#**(large) warns "in a**b, b may be too big" and return Infinity

Bug #3429: Integer#**(large) warns "in a**b, b may be too big" and return Infinity
http://redmine.ruby-lang.org/issues/show/3429

Author: Benoit Daloze
Status: Open, Priority: Normal
Category: core, Target version: 1.9.2
ruby -v: ruby 1.9.3dev (2010-06-09) [x86_64-darwin10.3.0]

Hi,

Trying to do
int**some_large_number can result in
"warning: in a**b, b may be too big"
#=> Infinity
By example,
2**7830457

It is not good behavior, as we can make a workaround and it works perfectly:
# 7830457 = 2 * 37 * 105817 - 1
n = (((2 ** 105817) ** 37) ** 2) / 2 # => ...8739992577 which is the good number

I think it is not consistent to return Infinity when a correct answer can be given.
And Integer**Integer should always return an Integer (Infinity is a Float)

Also, while doing some tests about this I noticed that "bignum == Float::INFINITY" or "bignum.infinite?" hangs, while it should not, as it is always false.

See the script attached for some details and a (nonsense) implementation Integer#int_pow method which show it is possible to get better results.


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