Rational, Fixnum#power! and negative values


#1

Hi all,

Another question about Rational#power!. I tried this

irb(main):001:0> 2.power!(-2)
NoMethodError: undefined method `power!’ for 2:Fixnum
from (irb):1
irb(main):002:0> require ‘rational’
=> true
irb(main):003:0> 2.power!(-2)
=> 0.25 # huh?

That returns 0.25. However, I would have expected Rational(1, 4).
Based on
the code in rational, it looks like power! is an alias for **, and ** is
an
alias for rpower. So, based on the rpower method, I would think that a
negative value for +other+ would call Rational.new! and return a
Rational.

Or do I have it wrong?

from rational.rb:

class Fixnum
undef quo

If Rational is defined, returns a Rational number instead of a

Fixnum.
def quo(other)
Rational.new!(self,1) / other
end
alias rdiv quo

Returns a Rational number if the result is in fact rational (i.e.

+other+
< 0).
def rpower (other)
if other >= 0
self.power!(other)
else
Rational.new!(self,1)**other
end
end

unless defined? 1.power!
alias power! **
alias ** rpower
end
end

Ideas? Thanks.

Dan


#2

Daniel B. wrote:

=> 0.25 # huh?
class Fixnum
if other >= 0
end

Ideas? Thanks.

Dan

power! is an alias of Fixnum::, then ** is reused as an alias of
rpower
So calling power! is not invoking rpower, it is invoking the original
Fixnum:

Took me a while to figure that out, the alias’ing does at first glance
look like it would chain the methods as you expected

Cheers