gistfile1.rb

require "bigdecimal"
# It would be nice if BigDecimal( BigDecimal("1") ) returned '1' as bigdecimal instead of an argument error, as it generally expects a String. 
#I ran into this problem upgrading a project to rails3 from rails2 that was using the old mysql adapter. In the conversion, we switched to mysql2 which auto converts query results to ruby-land types, hence BigDecimal(sql_decimal_result_that_used_to_be_a_string) will now fail as the adapter returns a BigDecimal. 
# The real world solution was to remove the BigDecimal wrapper around those sql queries, but the below was an interesting exercise nonetheless.


# BigDecimal("1") really means call a special global function 'BigDecimal' defined on Kernel. The C code is straight copy/pasta of BigDecimal.new  :[
# Make it go away
Kernel.send :remove_method, :BigDecimal

module Kernel
  class << self
    def BigDecimal_with_fix initial, digit=0
      if initial.is_a?(BigDecimal)
        return initial
      elsif initial.is_a?(Fixnum)
        return BigDecimal.new initial.to_s, digit
      end

      BigDecimal.new initial, digit
    end

    alias_method :BigDecimal, :BigDecimal_with_fix
  end
end

# Redefine the global BigDecimal function on Object and have it call our custom code above
class Object
  class_eval do
    def BigDecimal *args
      Kernel.BigDecimal *args
    end
  end
end