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

---
 queue.scm | 77 ++++++++++++++++++++++++++++++++++++++++++++++-----------------
 1 file changed, 57 insertions(+), 20 deletions(-)

(limited to 'queue.scm')

diff --git a/queue.scm b/queue.scm
index 89a65b0..820894f 100644
--- a/queue.scm
+++ b/queue.scm
@@ -1,21 +1,33 @@
-; "queue.scm"  Queues/Stacks for Scheme
-; Written by Andrew Wilcox (awilcox@astro.psu.edu) on April 1, 1992.
-;
-; This code is in the public domain.
+;; "queue.scm"  Queues/Stacks for Scheme
+;; Written by Andrew Wilcox (awilcox@astro.psu.edu) on April 1, 1992.
+;;
+;; This code is in the public domain.
 
 (require 'record)
 
-; Elements in a queue are stored in a list.  The last pair in the list
-; is stored in the queue type so that datums can be added in constant
-; time.
+;;@code{(require 'queue)}
+;;@ftindex queue
+;;
+;;A @dfn{queue} is a list where elements can be added to both the front
+;;and rear, and removed from the front (i.e., they are what are often
+;;called @dfn{dequeues}).  A queue may also be used like a stack.
+
+;; Elements in a queue are stored in a list.  The last pair in the list
+;; is stored in the queue type so that datums can be added in constant
+;; time.
 
 (define queue:record-type
   (make-record-type "queue" '(first-pair last-pair)))
+
+;;@args
+;;Returns a new, empty queue.
 (define make-queue
   (let ((construct-queue (record-constructor queue:record-type)))
     (lambda ()
       (construct-queue '() '()))))
 
+;;@args obj
+;;Returns @code{#t} if @var{obj} is a queue.
 (define queue? (record-predicate queue:record-type))
 
 (define queue:first-pair (record-accessor queue:record-type
@@ -27,21 +39,13 @@
 (define queue:set-last-pair! (record-modifier queue:record-type
 					      'last-pair))
 
+;;@body
+;;Returns @code{#t} if the queue @var{q} is empty.
 (define (queue-empty? q)
   (null? (queue:first-pair q)))
 
-(define (queue-front q)
-  (let ((first-pair (queue:first-pair q)))
-    (if (null? first-pair)
-	(slib:error "queue is empty" q))
-    (car first-pair)))
-
-(define (queue-rear q)
-  (let ((last-pair (queue:last-pair q)))
-    (if (null? last-pair)
-	(slib:error "queue is empty" q))
-    (car last-pair)))
-
+;;@body
+;;Adds @var{datum} to the front of queue @var{q}.
 (define (queue-push! q datum)
   (let* ((old-first-pair (queue:first-pair q))
 	 (new-first-pair (cons datum old-first-pair)))
@@ -50,6 +54,8 @@
 	(queue:set-last-pair! q new-first-pair)))
   q)
 
+;;@body
+;;Adds @var{datum} to the rear of queue @var{q}.
 (define (enqueue! q datum)
   (let ((new-pair (cons datum '())))
     (cond ((null? (queue:first-pair q))
@@ -59,6 +65,11 @@
     (queue:set-last-pair! q new-pair))
   q)
 
+;;@body
+;;@deffnx {Procedure} queue-pop! q
+;;Both of these procedures remove and return the datum at the front of
+;;the queue.  @code{queue-pop!} is used to suggest that the queue is
+;;being used like a stack.
 (define (dequeue! q)
   (let ((first-pair (queue:first-pair q)))
     (if (null? first-pair)
@@ -68,5 +79,31 @@
       (if (null? first-cdr)
 	  (queue:set-last-pair! q '()))
       (car first-pair))))
-
 (define queue-pop! dequeue!)
+
+;;@ All of the following functions raise an error if the queue @var{q}
+;;is empty.
+
+;;@body
+;;Removes and returns (the list) of all contents of queue @var{q}.
+(define (dequeue-all! q)
+  (let ((lst (queue:first-pair q)))
+    (queue:set-first-pair! q '())
+    (queue:set-last-pair!  q '())
+    lst))
+
+;;@body
+;;Returns the datum at the front of the queue @var{q}.
+(define (queue-front q)
+  (let ((first-pair (queue:first-pair q)))
+    (if (null? first-pair)
+	(slib:error "queue is empty" q))
+    (car first-pair)))
+
+;;@body
+;;Returns the datum at the rear of the queue @var{q}.
+(define (queue-rear q)
+  (let ((last-pair (queue:last-pair q)))
+    (if (null? last-pair)
+	(slib:error "queue is empty" q))
+    (car last-pair)))
-- 
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