Merge pull request #1755 from triska/doc

various smaller documentation improvements

src/lib/lists.pl

@@ -63,18 +63,16 @@ resource_error(Resource, Context) :-
 
 %% length(?Xs, ?N).
 %
-% Relates a list to its length (number of items). It can be used to count the elements of a current list or
+% Relates a list to its length (number of elements). It can be used to count the elements of a current list or
 % to create a list full of free variables with N length.
 %
 % ```
-% ?- length([a,b,c], 3).
+% ?- length("abc", 3).
 %    true.
-% ?- length([a,b,c], N).
+% ?- length("abc", N).
 %    N = 3.
 % ?- length(Xs, 3).
 %    Xs = [_A,_B,_C].
-% ?- length("chars", N).
-%    N = 5.
 % ```
 
 length(Xs0, N) :-
@@ -133,7 +131,8 @@ member(X, [_|Xs]) :- member(X, Xs).
 %
 % ```
 % ?- select(c, "abcd", X).
-%    X = "abd".
+%    X = "abd"
+% ;  false.
 % ```
 select(X, [X|Xs], Xs).
 select(X, [Y|Xs], [Y|Ys]) :- select(X, Xs, Ys).