tree: let tree-iter be iterable via generic iteration.

* lib.c (seq_iter_init_with_info): Recognize tree_iter object,
and treat using tree iterator function.

* tests/010/tree.tl: test case for tree subrange iteration
with collect-each.

* txr.1: Updated.

3 files changed, 36 insertions, 0 deletions

diff --git a/lib.c b/lib.c
index 45ec1417..3f2a9616 100644
--- a/lib.c
+++ b/lib.c
@@ -857,6 +857,16 @@ void seq_iter_init_with_info(val self, seq_iter_t *it,
         }
       }
     }
+    if (it->inf.obj->co.cls == tree_iter_s)
+    {
+      it->ui.iter = if3(support_rewind,
+                        copy_tree_iter(it->inf.obj),
+                        it->inf.obj);
+      it->ul.len = 0;
+      it->get = seq_iter_get_tree;
+      it->peek = seq_iter_peek_tree;
+      break;
+    }
     /* fallthrough */
   default:
     switch (it->inf.kind) {
diff --git a/tests/010/tree.tl b/tests/010/tree.tl
index b41e7973..06d02ce6 100644
--- a/tests/010/tree.tl
+++ b/tests/010/tree.tl
@@ -166,6 +166,11 @@
     (copy-search-tree tr) #T((identity < =) 1 2 3)
     (make-similar-tree tr) #T((identity < =))))
 
+(test
+  (collect-each ((el (tree-begin #T(() 1 2 3 4 5) 2 5)))
+    (* 10 el))
+  (20 30 40))
+
 (mtest
   (uni #T(() "a" "b") #T(() "b" "c")) ("a" "b" "c")
   (diff #T(() "a" "b") #T(() "b" "c")) ("a")
diff --git a/txr.1 b/txr.1
index af3fb16a..9f8dc04f 100644
--- a/txr.1
+++ b/txr.1
@@ -34636,6 +34636,14 @@ and
 are equivalent to
 .codn "(iter-begin X)" .
 
+Search trees are iterable. Iteration entails an in-order visits of the elements
+of a tree. A tree iterator created by
+.code tree-begin
+is also iterable. It is unspecified whether iteration over a
+.code tree-iter
+object modifies that object to perform the traversal, or whether it uses a copy
+of the iterator.
+
 If
 .code seq
 is not an iterable object, an error exception is thrown.
@@ -51866,6 +51874,19 @@ function to the returned
 .code tree-iter
 object.
 
+A
+.code tree-iter
+object is iterable.
+
+.TP* Example:
+
+.verb
+  (collect-each ((el (tree-begin #T(() 1 2 3 4 5)
+                                 2 5)))
+    (* 10 el))
+  --> (20 30 40)
+.brev
+
 .coNP Function @ tree-reset
 .synb
 .mets (tree-reset < iter < tree >> [ low-key <> [ high-key ]])