# Rational, Fixnum#power! and negative values

**URL:** <https://www.ruby-forum.com/t/rational-fixnum-power-and-negative-values/56261>\
**Category:** Ruby\
**Created:** [March 29, 2006, 10:08pm UTC](https://www.ruby-forum.com/t/rational-fixnum-power-and-negative-values/56261 "2006-03-29T22:08:24Z")\
**Posts on this page:** 2\
**Page:** 1

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**Author:** ![danielb](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/d/c57346/32.png) [@danielb](https://www.ruby-forum.com/u/danielb)\
**Post date:** [March 29, 2006, 10:08pm UTC](https://www.ruby-forum.com/t/rational-fixnum-power-and-negative-values/56261/1 "2006-03-29T22:08:24Z")

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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

---

<div class="post-metadata">

**Author:** ![danielb](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/d/c57346/32.png) [@danielb](https://www.ruby-forum.com/u/danielb)\
**Post date:** [March 29, 2006, 11:12pm UTC](https://www.ruby-forum.com/t/rational-fixnum-power-and-negative-values/56261/2 "2006-03-29T23:12:10Z")

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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