avl-tree-delete is a compiled Lisp function in `
(avl-tree-delete TREE DATA &optional TEST NILFLAG)
Delete the element matching DATA from the AVL tree TREE.
Matching uses the comparison function previously specified in
`avl-tree-create' when TREE was created.
Returns the deleted element, or nil if no matching element was
Optional argument NILFLAG specifies a value to return instead of
nil if nothing was deleted, so that this case can be
distinguished from the case of a successfully deleted null
If supplied, TEST specifies a test that a matching element must
pass before it is deleted. If a matching element is found, it is
passed as an argument to TEST, and is deleted only if the return
value is non-nil.