1:- module(func_issue_11, [count_unique/2]). 2:- use_module(library(func)). 3 4count_unique(L,N) :- 5 F = len of unique, 6 N = F $ L. 7 8len(X,N) :- 9 length(X,N). 10 11unique(XX,X) :- 12 sort(XX,X)