From: Ari Brown <ari@...>
Date: 2007-05-26T10:57:16+09:00
Subject: Ruby Math (nPr, nCr)

What's that? You want me to ask more questions? Sure!

So I'm writing a pascals triangle program. My goal is to write it in  
fewer lines than those on the RubyQuiz site. My idea is to use more  
math, and less programming.

So in order for my method to work, I sorta need to recreate nPr and  
nCr functions. To be official and learn more, I am doing this through  
a class. However, every time I run it, I get the following errors:

pascal.rb:29:in `pascal': undefined method `nCr' for 1:Fixnum  
(NoMethodError)
         from pascal.rb:24:in `upto'
         from pascal.rb:24:in `pascal'
         from pascal.rb:41

My code:

# Pascals triangle

class Integer

   def self.nPr(r)
     numerator   = factorial(self)
     denominator = factorial(self - r)

     @permutations = numerator / denominator
   end

   def self.nCr(r)
     numerator   = factorial(self)
     denominator = factorial(r) * factorial(self - r)

     @combinations = numberator / denominator
   end

end


def pascal max_row

   0.upto(max_row) {|row_num|

     holder = []
     ticker = 0
     while ticker != row_num
       result = row_num.nCr(ticker)
       ticker = ticker + 1
       holder = result.push
     end
     puts holder.join(' ').center(80)

   }

end

puts 'How many rows do you want?'
max_row = gets.chomp.to_i
pascal max_row


Any help?

Thanks,
Ari
--------------------------------------------|
If you're not living on the edge,
then you're just wasting space.