is_chinese()

# modified from http://stackoverflow.com/a/2728344
# iterate through all characters of a string
# returns true if all characters are chinese and false otherwise
def is_chinese(str)
    result = nil
    unless str.nil? 
        # put utf of each character in array
        list_of_chars = str.unpack("U*")
        # control if each character is a chinese character
        # breaks if find a non chinese character
        list_of_chars.each do |char|
            case char
                when 0x4E00..0x9FFF # main blocks
                    result = true
                when 0x3400..0x4DBF # extended block A
                    result = true
                when 0x20000..0x2A6DF # extended block B
                    result = true
                when 0x2A700..0x2B73F # extended block C
                    result = true
                when 0x2B740..0x2B81F # extended block D
                    result = true
                else
                    result = false
                    break
            end
        end
        return result
    end
end