tree: new tree-peek function.

* tree.c (tn_peek_next): New static function.
(tree_peek): New function.
(tree_init): Register tree-peek intrinsic.

* tree.h (tree_peek): Declared.

* txr.1: Documented.

* tests/010/tree.c: Work tree-peek into existing test case.

* share/txr/stdlib/doc-syms.tl: Updated.

1 files changed, 1 insertions, 0 deletions

diff --git a/tree.h b/tree.h
index d1b726c2..0ee9cb0a 100644
--- a/tree.h
+++ b/tree.h
@@ -48,5 +48,6 @@ val tree_begin_at(val tree, val lowkey);
 val tree_reset(val iter, val tree);
 val tree_reset_at(val iter, val tree, val lowkey);
 val tree_next(val iter);
+val tree_peek(val iter);
 val tree_clear(val tree);
 void tree_init(void);