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

---
 tsort.scm | 58 +++++++++++++++++++++++++++++++++++++++++++++++++++++-----
 1 file changed, 53 insertions(+), 5 deletions(-)

(limited to 'tsort.scm')

diff --git a/tsort.scm b/tsort.scm
index 9371f3c..9db98f2 100644
--- a/tsort.scm
+++ b/tsort.scm
@@ -1,7 +1,6 @@
 ;;; "tsort.scm" Topological sort
 ;;; Copyright (C) 1995 Mikael Djurfeldt
-;
-; This code is in the public domain.
+;;; This code is in the public domain.
 
 ;;; The algorithm is inspired by Cormen, Leiserson and Rivest (1990)
 ;;; "Introduction to Algorithms", chapter 23
@@ -9,7 +8,57 @@
 (require 'hash-table)
 (require 'primes)
 
-(define (topological-sort dag pred)
+;;@code{(require 'topological-sort)} or @code{(require 'tsort)}
+;;@ftindex topological-sort
+;;@ftindex tsort
+
+;;@noindent
+;;The algorithm is inspired by Cormen, Leiserson and Rivest (1990)
+;;@cite{Introduction to Algorithms}, chapter 23.
+
+;;@body
+;;@defunx topological-sort dag pred
+;;where
+;;@table @var
+;;@item dag
+;;is a list of sublists.  The car of each sublist is a vertex.  The cdr is
+;;the adjacency list of that vertex, i.e. a list of all vertices to which
+;;there exists an edge from the car vertex.
+;;@item pred
+;;is one of @code{eq?}, @code{eqv?}, @code{equal?}, @code{=},
+;;@code{char=?}, @code{char-ci=?}, @code{string=?}, or @code{string-ci=?}.
+;;@end table
+;;
+;;Sort the directed acyclic graph @1 so that for every edge from
+;;vertex @var{u} to @var{v}, @var{u} will come before @var{v} in the
+;;resulting list of vertices.
+;;
+;;Time complexity: O (|V| + |E|)
+;;
+;;Example (from Cormen):
+;;@quotation
+;;Prof. Bumstead topologically sorts his clothing when getting
+;;dressed.  The first argument to @0 describes which
+;;garments he needs to put on before others.  (For example,
+;;Prof Bumstead needs to put on his shirt before he puts on his
+;;tie or his belt.)  @0 gives the correct order of dressing:
+;;@end quotation
+;;
+;;@example
+;;(require 'tsort)
+;;@ftindex tsort
+;;(tsort '((shirt tie belt)
+;;         (tie jacket)
+;;         (belt jacket)
+;;         (watch)
+;;         (pants shoes belt)
+;;         (undershorts pants shoes)
+;;         (socks shoes))
+;;       eq?)
+;;@result{}
+;;(socks undershorts pants shoes watch shirt belt tie jacket)
+;;@end example
+(define (tsort dag pred)
   (if (null? dag)
       '()
       (let* ((adj-table (make-hash-table
@@ -42,5 +91,4 @@
 			    (visit (car def) (cdr def)))))
 		    (cdr dag)))
 	sorted)))
-
-(define tsort topological-sort)
+(define topological-sort tsort)
-- 
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