Command line executable which searches for the first occurence of a given string in PI, in the form of an ascii base10 string.

find_in_pi.rb

#!/usr/bin/env ruby
# encoding: utf-8
# 
# Created by Nat Noordanus on 2012-10-20.
# 

# requires a text file of digits of pi http://stuff.mit.edu/afs/sipb/contrib/pi/pi-billion.txt

def find_in_pi string, pi_file_path
  # convert string to base 10 ascii
  bin_string = string.each_char.map{|c| c.ord.to_s(2) }.join
  b10_string = Integer("0b#{bin_string}").to_s
  
  puts "Searching for #{b10_string} in pi..."
  
  # stream pi and scan for target
  pi_file = File.open(pi_file_path,'r')
  
  match_length = 0
  i = -2 # start counting from zero at the firs decimal characters
  pi_file.each_char do |c|
    i += 1
    if c == b10_string[match_length] and (match_length+=1) == b10_string.length
      puts "String found at Pi*10^-#{i}."
      return
    end 
    match_length = 0
  end
  puts "String not found within #{i} digits."  
end

find_in_pi ARGV.join(" "), "./pi-billion.txt"