Hi community,

I am a bit confused why in `test7`

i get a second solution in which `IN`

is` [p(A), p(A)]`

. This does not happen with nth1/4 as shown in `test8`

. Does select/3 somehow unify `p(A)`

and `p(B)`

?

Cheers/JCR

```
test7:-
IN = [p(A), p(B)],
select(p(A), IN, OUT),
numbervars(IN, 0, _),
numbervars(OUT, 0, _),
format('~w~w~n', ['IN is ', IN]),
format('~w~w~n', ['OUT is ', OUT]).
test8:-
IN = [p(A), p(B)],
between(1, 2, IND),
nth1(IND, IN, _, OUT),
numbervars(IN, 0, _),
numbervars(OUT, 0, _),
format('~w~w~n', ['IN is ', IN]),
format('~w~w~n', ['OUT is ', OUT]).
```

OUTPUT:

```
?- test7.
IN is [p(A),p(B)]
OUT is [p(B)]
true ;
IN is [p(A),p(A)]
OUT is [p(A)]
true.
```

```
?- test8.
IN is [p(A),p(B)]
OUT is [p(B)]
true ;
IN is [p(A),p(B)]
OUT is [p(A)]
true.
```