Hi Roberto,

I am trying to write some portable code and, in foreign code, I need to know what is the maximum integer value that can be passed to PL_put_integer().

Am I correct if I say that the right way to know that value is by calling

 PL_query(PL_QUERY_MAX_INTEGER)

Yip. Please note that since quite a while SWI-Prolog's integers are C longs and can represent all values a C long can.

and that I need not be concerned with the PL_QUERY_MAX_TAGGED_INT query that is defined a couple of lines later in SWI-Prolog.h?

Yip. This returns the maximum value that is stored efficiently on the stacks (the space required for integers appearing in a clause is always the same).

Cheers --- Jan