I have no idea what this field is for

array_elements_diff.rb

# my first serious ruby question in like forever: 

class Array
  def token_diff(other)
    memo = 0 
    self.each_with_index do |element, index|
      memo += 1 if other[index] != element
    end 
    return memo
  end
end

# this works only for the naïvest of cases:
# >> [:a, :b, :c].token_diff([:a, :b, :c])
# => 0
# >> [:a, :b, :c].token_diff([:a, :b])
# => 1
# >> [:a, :b, :c].token_diff([:a])
# => 2

# and fails...
# >> [:a, :b].token_diff([:a, :b, :c])
# => 0

# I know there are better, more elegant ways to do this, but I'm stumped. halp!!!1

What about something like this?

class Array
  def token_diff(other)
    if size > other.size
      base = self
    else
      base, other = other, self
    end

    base.zip(other).count { |a, b| a != b }
  end
end

I'll try that.

just in case, real specs:

token_diff([:a, [[:b, [:c, "d"], [:c, "e"]], [:f, "g"]]], [:a, [[:b, [:c, "d"], [:c, "e"]], [:f, "g"]]]).should == 0
token_diff([:a, [[:b, [:c, "d"], [:c, "e"]], [:f, "g"]]], [:a, [[:b, [:c, "d"], [:c, "e"]], [:f, "h"]]]).should == 1

I get a no method error for count. Is that 1.9? I'm using 1.8.

there's an implementation here http://blade.nagaokaut.ac.jp/cgi-bin/scat.rb/ruby/ruby-talk/75193

and also:

a = [:a, [[:b, [:c, "d"], [:c, "e"]], [:f, "g"]]]
b = [:a, [[:c, "h"], [:a, [[:b, [:c, "d"], [:c, "e"]], [:f, "g"]]]]]
token_diff(a, b).should == 1

a = [:a, [[:b, [:c, "d"], [:c, "e"]], [:f, "g"]]]
b = [:a, [[:c, "h"], [:a, [[:b, [:c, "d"], [:c, "e"]], [:f, "i"]]]]]
token_diff(a, b).should == 2

if (list1.size > list2.size) (list1 - (list1 & list2)).size else list2 - (list2 & list1).size() end

Try that one too.

I don't understand

a = [:a, [[:b, [:c, "d"], [:c, "e"]], [:f, "g"]]]
b = [:a, [[:c, "h"], [:a, [[:b, [:c, "d"], [:c, "e"]], [:f, "i"]]]]]
token_diff(a, b).should == 2

Both a and b have 2 elements; the first element of each is :a.