From 8466d8cfa486fb30d1755c4261b781135083787b Mon Sep 17 00:00:00 2001
From: Bryan Newbold <bnewbold@robocracy.org>
Date: Mon, 20 Feb 2017 00:05:29 -0800
Subject: Import Upstream version 3a1

---
 tree.scm | 69 +++++++++++++++++++++++++++++++++++++++++++++++++---------------
 1 file changed, 53 insertions(+), 16 deletions(-)

(limited to 'tree.scm')

diff --git a/tree.scm b/tree.scm
index e9bc999..ae29a52 100644
--- a/tree.scm
+++ b/tree.scm
@@ -5,15 +5,39 @@
 
 ;; Deep copy of the tree -- new one has all new pairs.  (Called
 ;; tree-copy in Dybvig.)
-(define (tree:copy-tree tree)
-  (if (pair? tree)
-      (cons (tree:copy-tree (car tree))
-	    (tree:copy-tree (cdr tree)))
-      tree))
+
+;;@code{(require 'tree)}
+;;@ftindex tree
+;;
+;;These are operations that treat lists a representations of trees.
 
 ;; Substitute occurrences of old equal? to new in tree.
 ;; Similar to tree walks in SICP without the internal define.
-(define (tree:subst new old tree . equ?)
+
+;; substq and substv aren't in CL.  (Names from Dybvig)
+
+;;@args new old tree
+;;@args new old tree equ?
+;;@code{subst} makes a copy of @3, substituting @1 for
+;;every subtree or leaf of @3 which is @code{equal?} to @2
+;;and returns a modified tree.  The original @3 is unchanged, but
+;;may share parts with the result.
+;;
+;;@code{substq} and @code{substv} are similar, but test against @2
+;;using @code{eq?} and @code{eqv?} respectively.  If @code{subst} is
+;;called with a fourth argument, @var{equ?} is the equality predicate.
+;;
+;;Examples:
+;;@lisp
+;;(substq 'tempest 'hurricane '(shakespeare wrote (the hurricane)))
+;;   @result{} (shakespeare wrote (the tempest))
+;;(substq 'foo '() '(shakespeare wrote (twelfth night)))
+;;   @result{} (shakespeare wrote (twelfth night . foo) . foo)
+;;(subst '(a . cons) '(old . pair)
+;;       '((old . spice) ((old . shoes) old . pair) (old . pair)))
+;;   @result{} ((old . spice) ((old . shoes) a . cons) (a . cons))
+;;@end lisp
+(define (subst new old tree . equ?)
   (set! equ? (if (null? equ?) equal? (car equ?)))
   (letrec ((walk (lambda (tree)
 		   (cond ((equ? old tree) new)
@@ -22,16 +46,29 @@
 				(walk (cdr tree))))
 			 (else tree)))))
     (walk tree)))
-
-;; The next 2 aren't in CL.  (Names from Dybvig)
-
-(define (tree:substq new old tree)
+(define (substq new old tree)
   (tree:subst new old tree eq?))
-
-(define (tree:substv new old tree)
+(define (substv new old tree)
   (tree:subst new old tree eqv?))
 
-(define copy-tree tree:copy-tree)
-(define subst tree:subst)
-(define substq tree:substq)
-(define substv tree:substv)
+;;@body
+;;Makes a copy of the nested list structure @1 using new pairs and
+;;returns it.  All levels are copied, so that none of the pairs in the
+;;tree are @code{eq?} to the original ones -- only the leaves are.
+;;
+;;Example:
+;;@lisp
+;;(define bar '(bar))
+;;(copy-tree (list bar 'foo))
+;;   @result{} ((bar) foo)
+;;(eq? bar (car (copy-tree (list bar 'foo))))
+;;   @result{} #f
+;;@end lisp
+(define (copy-tree tree)
+  (if (pair? tree)
+      (cons (tree:copy-tree (car tree))
+	    (tree:copy-tree (cdr tree)))
+      tree))
+
+(define tree:copy-tree copy-tree)
+(define tree:subst subst)
-- 
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