tree: streamline iteration; provide high limit.

Getting rid of tree-begin-at and tree-reset-at. Now tree-begin
takes two optional parameters, for specifying high and low
range.

* tree.c (struct tree_diter): New members, tree and highkey.
We need tree due to requiring access to the less function.
If the iterator has no highkey, the iterator itself is stored
in that member to indicate this.
(tree_iter_mark): Mark the tree and highkey.
(tree_begin): Take optional lowkey and highkey arguments,
initializing iterator acordingly.
(tree_begin_at): Function removed.
(copy_tree_iter, replace_tree_iter): Copy tree and highkey
members. The latter require special handling due to the funny
convention for indicating highkey absence.
(tree_reset): Take optional lowkey and highkey arguments,
configuring these in the iterator being reset.
(tree_reset_at): Function removed.
(tree_next, tree_peek): Implement highkey semantics.
(sub_tree): Simplified: from and to
arguments are just passed through to tree_begin, and there is
no need for a separate loop which enforces the upper limit,
that now being handled by the iterator itself.
(tree_begin): Update registrations of tree-begin and
tree-reset; remove tree-begin-at and tree-reset-at intrinsics.

* tree.h (tree_begin_at, tree_reset_at): Declarations removed.
(tree_begin, tree_reset): Declarations updated.

* lib.c (seq_iter_rewind, seq_iter_init_with_info, where,
populate_obj_hash): Default new optional arguments in
tree_begin and tree_reset calls.

* parser.c (circ_backpatch): Likewise.

* tests/010/tree.tl: Affected cases updated.

* txr.1: Documentation updated.

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

1 files changed, 2 insertions, 4 deletions

diff --git a/tree.h b/tree.h
index 072bc6df..f883b8c7 100644
--- a/tree.h
+++ b/tree.h
@@ -48,12 +48,10 @@ val tree_lookup_node(val tree, val key);
 val tree_lookup(val tree, val key);
 val tree_delete_node(val tree, val key);
 val tree_delete(val tree, val key);
-val tree_begin(val tree);
-val tree_begin_at(val tree, val lowkey);
+val tree_begin(val tree, val lowkey, val highkey);
 val copy_tree_iter(val iter);
 val replace_tree_iter(val diter, val siter);
-val tree_reset(val iter, val tree);
-val tree_reset_at(val iter, val tree, val lowkey);
+val tree_reset(val iter, val tree, val lowkey, val highkey);
 val tree_next(val iter);
 val tree_peek(val iter);
 val tree_clear(val tree);