require 'wcswidth/kernel_method'
# full width chars
wcswidth("！") # => 2
wcswidth("一") # => 2
# single width chars
wcswidth("A") # => 1
wcswidth("·") # => 1
# zero width chars
wcswidth("ֿ") # => 0
wcswidth("\0") # => 0
# control chars
wcswidth("\x01") # => -1
wcswidth("\n") # => -1