[m-users.] A predicate taking a lists of predicates as input?

[Sean Charles (emacstheviking)]

Ah yes! Sometimes a question mark is just a question mark!

I often create predicates with names like `S0->S1` or `EOT`, `SOM`, fits my mood some days.



> On 21 Sep 2025, at 23:12, Anders Lundstedt <mercury-users at anderslundstedt.se> wrote:
> 
>> I just scanned Chapter 8, Higher Order... what is the meaning of the question marks here? I could find no reference.
>> 
>> :- pred ?(list(ta_rule(TKNS)), TKNS, TKNS).
> 
> ‘?’ just denotes the name of the predicate. If one would prefer, one
> could replace ‘?’ with, for example, ‘optional’.