Chris Hulan
3/29/2006 9:06:00 PM
Daniel Berger wrote:
> 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
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