sub: don't produce an iterator.

Having the sub function yield an iterator in some cases
is a defective requirement, causing problems like this:

  1> (partition 1..10 '(2 3))
  ((1 2) (3) #<seq-iter: a24c380>)

With fix:

  1> (partition 1..10 '(2 3))
  ((1 2) (3) (4 5 6 7 8 9))

* lib.c (sub_iter): When the interval is open and we are
operating on a sequence via iter-begin, do not return an
iterator. Convert it to a lazy list. Not subjecting this to -C
compat flag; I can't imagine anyone writing code to depend on
this, rather than stepping around it as a bugx.

* txr.1: Documentation updated.

2 files changed, 4 insertions, 4 deletions

diff --git a/lib.c b/lib.c
index 8418844a..52f984e3 100644
--- a/lib.c
+++ b/lib.c
@@ -3014,7 +3014,7 @@ static val sub_iter(val obj, val from, val to)
   if (!to) {
     do {
       if (ge(idx, from))
-        return iter_dynamic(&iter);
+        return list_seq(iter_dynamic(&iter));
       idx = succ(idx);
     } while (seq_get(&iter, &elem));
   } else {
diff --git a/txr.1 b/txr.1
index bda03dcc..c18ee4ce 100644
--- a/txr.1
+++ b/txr.1
@@ -34701,14 +34701,14 @@ argument may also be any other object type that is suitable as input to the
 .code iter-begin
 function. In this situation, assigning to
 .code sub
-syntax produces an error. The behavior is complex. In cases where the
+syntax produces an error. Furthermore, in cases where the
 .meta from
 and
 .meta to
 arguments imply that a suffix of
 .meta sequence
-is required, an iterator may be returned which traverses the suffix
-of the sequence. In other cases, a list of the elements selected by
+is required, an lazy list of the suffix of the iterated sequence
+will be returned. In other cases, a regular list of the elements selected by
 .code sub
 is returned.