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<07e4e441-f981-4034-998b-c665ee434501n@googlegroups.com> 79643c51
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@REPLYADDR Mild Shock <bursejan@gmail.com>
@REPLYTO 2:5075/128 Mild Shock
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@TZUTC: -0700
@PID: G2/1.0
@TID: FIDOGATE-5.12-ge4e8b94
Did you know that Novacore has change_arg/3?
Works for Dogelog Player and formerly Jekejeke Prolog.
It is similar like nb_linkarg/3 in SWI-Prolog.

So we can implement countall/3 in a blink:

countall(G, N) :-
   functor(Holder, v, 1),
   change_arg(1, Holder, 0),
   (G,
       arg(1, Holder, H),
       J is H+1,
       change_arg(1, Holder, J),
       fail; true),
   arg(1, Holder, N).

Works find:

?- countall(between(10,20,_), N).
N = 11.
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