branch: externals/heap
commit 596261cb05a2c1b47975ffe2935b40a2efac7a7a
Author: Toby S. Cubitt <toby-predict...@dr-qubit.org>
Commit: Toby S. Cubitt <toby-predict...@dr-qubit.org>
Implement iterator generators on collection data structures.
---
heap.el | 32 ++++++++++++++++++++++++++------
1 file changed, 26 insertions(+), 6 deletions(-)
diff --git a/heap.el b/heap.el
index b522aa7..e1c03dc 100644
--- a/heap.el
+++ b/heap.el
@@ -1,7 +1,7 @@
;; -*- lexical-binding: t; -*-
;;; heap.el --- Heap (a.k.a. priority queue) data structure
-;; Copyright (C) 2004-2006, 2008, 2012-2013 Free Software Foundation, Inc
+;; Copyright (C) 2004-2006, 2008, 2012-2013, 2017 Free Software Foundation,
Inc
;; Author: Toby Cubitt <toby-predict...@dr-qubit.org>
;; Version: 0.4
@@ -46,8 +46,8 @@
;; advance. Although the heap will grow dynamically if it becomes full, this
;; requires copying the entire heap, so insertion has worst-case complexity
;; O(n) instead of O(log n), though the amortized complexity is still
-;; O(n). (For applications where the maximum size of the heap is not known in
-;; advance, an implementation based on binary trees might be more suitable,
+;; O(log n). (For applications where the maximum size of the heap is not known
+;; in advance, an implementation based on binary trees might be more suitable,
;; but is not currently implemented in this package.)
;;
;; You create a heap using `make-heap', add elements to it using `heap-add',
@@ -62,6 +62,11 @@
(eval-when-compile (require 'cl))
+(defmacro heap--when-generators (then)
+ "Evaluate THEN if `generator' library is available."
+ (declare (debug t))
+ (if (require 'generator nil 'noerror) then))
+
;;; ================================================================
;;; Internal functions for use in the heap package
@@ -165,7 +170,7 @@ defaulting to 2."
"Return a copy of heap HEAP."
(let ((newheap (heap--create (heap--cmpfun heap) (heap--size heap)
(heap--resize heap))))
- (setf (heap--vect newheap) (vconcat (heap--vect heap) [])
+ (setf (heap--vect newheap) (vconcat (heap--vect heap))
(heap--count newheap) (heap--count heap))
newheap))
@@ -276,8 +281,8 @@ RESIZE-FACTOR sets the factor by which the heap's size is
increased if it runs out of space, defaulting to 2."
(or resize-factor (setq resize-factor 2))
(let ((heap (heap--create compare-function (length vec) resize-factor))
- (i (ceiling (1- (expt 3
- (ceiling (1- (log (1+ (* 2 (length vec))) 3))))) 2)))
+ (i (ceiling
+ (1- (expt 3 (ceiling (1- (log (1+ (* 2 (length vec))) 3))))) 2)))
(setf (heap--vect heap) vec
(heap--count heap) (length vec))
(while (>= (decf i) 0) (heap--sift-down heap i))
@@ -308,6 +313,21 @@ Return number of entries removed."
(heap--count heap) 0)))
+(heap--when-generators
+ (iter-defun heap-iter (heap)
+ "Return a heap iterator object.
+
+Calling `iter-next' on this object will retrieve the next element
+from the heap. The heap itself is not modified.
+
+\(Note that in this heap implementation, constructing a heap
+iterator is not very efficient, taking O(n) time for a heap of
+size n. Each call to `iter-next' on the other hand *is*
+efficient, taking O(log n) time.\)"
+ (let ((heap (heap-copy heap)))
+ (while (not (heap-empty heap))
+ (iter-yield (heap-delete-root heap))))))
+
(provide 'heap)
