Ridiculous Adding

ridiculous_adding.rb

# Add two numbers in Ruby.
# Strategy: make a list of known sums, and look up the one in question.

# What's the point? The point is: nowadays computing machinery is so powerful that 
# implementation in many cases doesn't matter. The most ridiculous approach can still be
# useful, and improving it, a waste of time.

# So here's a very silly way how to add numbers.

def add_by_grep(a,b)
  sums = []
  1000.times do |x| 
    1000.times do |y| 
      sums << "#{x}+#{y}=#{x+y}"
    end 
  end 

  matches = sums.grep /\A#{a}\+#{b}=\d+\Z/
  case matches.size
    when 0
      raise "Don't know"
    when 1
      matches.first =~ /\A#{a}\+#{b}=(\d+)\Z/
      return $1.to_i
    else
      raise "Unexpected error. More than one match! #{matches.inspect}" 
  end 
end

Sample usage:

$ irb
1.9.3p392 :033 > require '/tmp/ridiculous_adding.rb'
=> true
1.9.3p392 :034 > s = Time.new; puts add_by_grep(12,99); puts "Took #{Time.new - s} seconds"
111
Took 1.313211 seconds

So still faster than a human in most cases.

Caching does improve the timing though. I'm getting it down to 0.4 secs, when reusing the "sums" array