adding tree package to be used for atoms, etc

tree.lisp

@@ -0,0 +1,47 @@
+;;; -*- Mode: Lisp;  show-trailing-whitespace: t; Base: 10; indent-tabs: nil; Syntax: ANSI-Common-Lisp; Package: TREE; -*-
+;;; Copyright (c) 2013, Mark VandenBrink. All rights reserved.
+(in-package #:tree)
+
+(defun make-node (data)
+  "Creates a new node with DATA as contents"
+  (cons (cons data nil) nil))
+
+(defun add-child (node child)
+  "Takes two nodes created with MAKE-NODE and adds CHILD"
+  (nconc (first node) child)
+  node)
+
+(defun first-child (node)
+  "Returns a reference to the first child of NODE"
+  (rest (first node)))
+
+(defun next-sibling (node)
+  "Returns next SIBLING of NODE"
+  (rest node))
+
+(defun data (node)
+  "Returns the information in NODE"
+  (first (first node)))
+
+(defun traverse (tree func &optional (depth 0))
+  "Depth-first traversal of TREE calling FUNC for each node"
+  (when tree
+    (funcall func (data tree) depth)
+    (traverse (first-child tree) func  (+ 2 depth))
+    (traverse (next-sibling tree) func depth)))
+
+(defun print-tree (tree)
+  "Print the nodes of TREE"
+  (traverse tree (lambda (node depth) (format t "~v@tNode: ~a~%" depth node))))
+
+(defun find-tree (tree test)
+  "Find all nodes in TREE where TEST returns T"
+  (let ((results))
+    (traverse tree (lambda (node depth)
+                     (declare (ignore depth))
+                     (when (funcall test node)
+                       (push node results))))
+    (nreverse results)))
+
+(let ((pkg (find-package :tree)))
+  (do-all-symbols (sym pkg) (when (eql (symbol-package sym) pkg) (export sym pkg))))