class Cucumber::StepMatch

def replace_arguments(string, step_arguments, format, &proc)
  s = string.dup
  offset = past_offset = 0
  step_arguments.each do |step_argument|
    next if step_argument.offset.nil? || step_argument.offset < past_offset
    
    replacement = if block_given?
      proc.call(step_argument.val)
    elsif Proc === format
      format.call(step_argument.val)
    else
      format % step_argument.val
    end
    s[step_argument.offset + offset, step_argument.val.length] = replacement
    offset += replacement.unpack('U*').length - step_argument.val.unpack('U*').length
    past_offset = step_argument.offset + step_argument.val.length
  end
  s
end