Prolog: “findall” for limited number of solutions

Question

Say I want to find sum of all solutions to a predicate, I just can use

findall(L, find(L), Sols),

and just sum members of Sols.

But

Answer 1

Needing to make a thread-safe solution in SWI Prolog, I came with this:

find_n( N, Solution, Goal, Solutions ) :-
    thread_self( Thread_id ),
    atomic_list_concat( [counter, Thread_id], Counter_flag_key ),
    flag( Counter_flag_key, _, 0 ),

    findall( Solution, (

        call( Goal ),

        flag( Counter_flag_key, X, X ),
        X1 is X + 1,
        flag( Counter_flag_key, _, X1 ),

        ( X1 >= N -> !; true )

    ), Solutions ).