As you are splitting of a single byte only, you already covered most available whitespace. In that range there is only \v and \r missing AFAIR…

A better approach that you can extend to work with all whitespace is this one:

def f(<<h :: utf8, tail::binary>> when h not in ~c[ \t\n\r\v…], do…

You can find a list of all characters that are marked as whitespace by the unicode standard in wikipedia:

As of Unicode 12.1 the following are categorised as whitespace (a list of code point ranges in this representation):

iex> Cldr.Unicode.Category.categories[:Zs] 
[
  {32, 32},
  {160, 160},
  {5760, 5760},
  {8192, 8202},
  {8239, 8239},
  {8287, 8287},
  {12288, 12288}
]

I have a lib that defines some guards to help with this sort of thing but specifically for whitespace you can:

when codepoint == 32 or codepoint == 160 or codepoint == 5760 or codepoint in 8192..8202 or codepoint == 8239 or codepoint == 8287 or codepoint == 12288

Or in a regex you can match on Unicode character categories:

iex> Regex.match? ~r/\p{Zs}/u, "   "
true

"\u00a0" as a string, or ~c[\u00a0] as charlist (with singlequote syntax as well).

Thanks! What’s your lib? It sounds relevant.