op/3 current_op/3 failure

[flexoron]

?- op(1,xfx,'is-').
   true.
?- current_op(1,X,Y).
   false. % unexpected
?-

[triska]

$ scryer-prolog 
?- use_module(library(lists)).
   true.
?- length(_, Pri), current_op(Pri, Fix, Op).
   error(domain_error(operator_priority,1201),op/3).

So, no operator of any given priority exists?

Note that it is not unexpected that a domain error arises eventually. But it is unexpected that no solutions are found.