gistfile1.rb

    # 004
    sorted_rates = rates.select { |rate| rate.from != 'USD' }.
                         sort   { |a, b| a.from <=> from_cur }.
                         map    { |rate| [rate] }
    
    # Split the select into two? less efficient but "single responsibility" ?
    all_paths(sorted_rates).select { |rates_arr| rates_arr.first.from == from_cur && rates_arr.last.to == 'USD' }.
                            sort   { |a, b| a.length <=> b.length }.
                            first
    
    all_paths(sorted_rates).select { |rates_arr| rates_arr.last.to == 'USD' }.
                            select { |rates_arr| rates_arr.first.from == from_cur }.
                            sort   { |a, b| a.length <=> b.length }.
                            first

    # Does this actually change what is in "paths"
    left_arr << right_arr.first                   
    
    
    # 007
      def find_common_currency(from, to, table)
        table[from].keys.each do |k|
          return k if table[k].has_key?(to)
        end
        return nil
      end
  
      def find_common_currency(from, to, table)
        table[from].keys.find { |k| table[k].has_key?(to) }
      end
    
    
  # 005  
  # Unusual to have require_relative INSIDE a class definition
  
  require_relative 'international_trade/sales_transactions'
  require_relative 'international_trade/currency_conversion_table'

  # Can use select instead of reject and a != (double negatives)
  sku_items = transactions.reject {|t| t if t.sku != sku }
  
  # Do you really mean InternationalTrade to be a Module? -- it has no behavior or state of its own
  class InternationalTrade
    class CurrencyConversionTable
    
  # This seems like it shouldn't be burried inside CurrencyConversionTable class but at the module level
  # unless it is only an internal implementation detail
  
  class ConversionItem