Are all unicode digit characters classified?

Are all unicode digit characters classified? I am trying to use Unicode subscript codes like:

?- atom_codes('₁₂₃', X).
X = [8321, 8322, 8323].

But somehow I cannot use the codes in a variable:

?- X = A₀.
ERROR: Syntax error: Operator expected
ERROR: ** here **
ERROR: A₀ . 

Subscript would be handy… The Prolog system could see A₀ like it sees A0:

?- X = A0.
X = A0.

There’s 103354 prolog_identifier_continues, but ₀ ain’t one of them.

?- aggregate_all(count, code_type(_, prolog_identifier_continue), N).
N = 103354.

?- char_type(₀, Type).
Type = graph ;
Type = to_lower('₀') ;
Type = to_upper('₀') ;

Hmm, I am also on a mac right now:

?- char_type(₂, Type).
Type = graph ;
Type = to_lower('₂') ;
Type = to_upper('₂') ;

Maybe we have discovered at least one pragmatic reason to stick to ascii…

Graph is fine, “produces a visible mark on a page when printed”. But also in the docs:

The types are sensititve to the active locale , see setlocale/3


The types prolog_var_start , prolog_atom_start , prolog_identifier_continue and prolog_symbol are based on the locale-independent built-in classification routines that are also used by read/1 and friends.

Every time I start looking at unicode I end up backing off cautiously.