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-rw-r--r--priorque.scm73
1 files changed, 34 insertions, 39 deletions
diff --git a/priorque.scm b/priorque.scm
index 0ad3007..9f1591f 100644
--- a/priorque.scm
+++ b/priorque.scm
@@ -8,7 +8,7 @@
;1. Any copy made of this software must include this copyright notice
;in full.
;
-;2. I have made no warrantee or representation that the operation of
+;2. I have made no warranty or representation that the operation of
;this software will be error-free, and I am under no obligation to
;provide any services, by way of maintenance, update, or otherwise.
;
@@ -17,21 +17,20 @@
;promotional, or sales literature without prior written consent in
;each case.
-;;; Algorithm from:
-;;; Introduction to Algorithms by T. Cormen, C. Leiserson, R. Rivest.
-;;; 1989 MIT Press.
+;;@code{(require 'priority-queue)}
+;;@ftindex priority-queue
+;;
+;;@noindent
+;;This algorithm for priority queues is due to
+;;@cite{Introduction to Algorithms}
+;;by T. Cormen, C. Leiserson, R. Rivest.
+;;1989 MIT Press.
(require 'record)
;; Record type.
(define heap:rtd (make-record-type "heap" '(array size heap<?)))
-;; Constructor.
-(define heap:make-heap
- (let ((cstr (record-constructor heap:rtd)))
- (lambda (pred<?)
- (cstr (make-vector 4) 0 pred<?))))
-
;; Reference an element.
(define heap:ref
(let ((ra (record-accessor heap:rtd 'array)))
@@ -55,10 +54,6 @@
(vector-set! ra i (vector-ref ra j))
(vector-set! ra j tmp)))))
-
-;; Get length.
-(define heap:length (record-accessor heap:rtd 'size))
-
(define heap:heap<? (record-accessor heap:rtd 'heap<?))
(define heap:set-size!
@@ -92,7 +87,24 @@
(heap:exchange a i largest)
(heap:heapify a largest)))))
-(define (heap:insert! a key)
+;;;; Externals
+
+;;@body
+;;Returns a binary heap suitable which can be used for priority queue
+;;operations.
+(define make-heap
+ (let ((cstr (record-constructor heap:rtd)))
+ (lambda (pred<?)
+ (cstr (make-vector 4) 0 pred<?))))
+
+;;@args heap
+;;Returns the number of elements in @1.
+(define heap-length (record-accessor heap:rtd 'size))
+
+;;@args heap item
+;;Inserts @2 into @1. @2 can be inserted multiple
+;;times. The value returned is unspecified.
+(define (heap-insert! a key)
(define i (+ 1 (heap:length a)))
(heap:set-size! a i)
(do ()
@@ -102,7 +114,11 @@
(set! i (heap:parent i)))
(heap:set! a i key))
-(define (heap:extract-max! a)
+;;@args heap
+;;Returns the item which is larger than all others according to the
+;;@var{pred<?} argument to @code{make-heap}. If there are no items in
+;;@1, an error is signaled.
+(define (heap-extract-max! a)
(if (< (heap:length a) 1)
(slib:error "heap underflow" a))
(let ((max (heap:ref a 1)))
@@ -111,26 +127,5 @@
(heap:heapify a 1)
max))
-;;
-;; Externals.
-;;
-(define make-heap heap:make-heap)
-(define heap-insert! heap:insert!)
-(define heap-extract-max! heap:extract-max!)
-(define heap-length heap:length)
-
-(define (heap:test)
- (require 'debug)
- (let ((heap #f))
- (set! heap (make-heap char>?))
- (heap-insert! heap #\A)
- (heap-insert! heap #\Z)
- (heap-insert! heap #\G)
- (heap-insert! heap #\B)
- (heap-insert! heap #\G)
- (heap-insert! heap #\Q)
- (heap-insert! heap #\S)
- (heap-insert! heap #\R)
- (do ((i 7 (+ -1 i)))
- ((negative? i))
- (write (heap-extract-max! heap)) (newline))))
+;; Internal protect.
+(define heap:length heap-length)