这是问题所在:
$ swipl
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For help, use ?- help(Topic). or ?- apropos(Word).
?- use_module(library(clpfd)).
true.
?- N in 1..3, length(L, N).
N = 1,
L = [_G1580] ;
N = 2,
L = [_G1580, _G1583] ;
N = 3,
L …