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.

1 files changed, 21 insertions, 0 deletions

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 ]])