domains
i = integer
list_i = i*
list_l = list_i*
predicates
nondeterm leng(list_i,i)
nondeterm index(list_l,i,list_i)
nondeterm vvd(list_l,list_l)

clauses

index([L|LL],1,L).
index([L|LL],N,Result):-X=N-1, index(LL,X,Result).

leng([],0).
leng([_|L],Res):-leng(L,R), Res=R+1.

vvd([L1],[]):-leng(L1,N),index([L1|L],N,L2),L1=L2.
vvd([L1],[L1]):-leng(L1,N),index([L1|L],N,L2),not(L1=L2).
vvd([L1|L], Res):-leng(L1,N),index([L1|L],N,L2),not(L1=L2),Res=[L1|R],vvd(L,R).
vvd([L1|L], Res):-leng(L1,N),index([L1|L],N,L2),L1=L2,Res=R,vvd(L,R).

goal
%vvd([[1],[1],[1]],Result).
%index([[1,2,3],[4,5],[6]],2,Res).
%leng([8,2,3,5],Res).