* Fix for calculating large factorials
@ 2017-04-18 8:44 michael schuldt
2017-04-18 18:28 ` Paul Eggert
0 siblings, 1 reply; 2+ messages in thread
From: michael schuldt @ 2017-04-18 8:44 UTC (permalink / raw)
To: emacs-devel
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I was playing around with calc bignums and found that calculating the
factorial of
large numbers results in the error "Variable binding depth exceeds
max-specpdl-size".
I though this might be a good chance to try out the contribution process,
I've attached
a path which simply eliminates the troublesome recursiveness of
math-factorial-iter.
-Michael
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From 9cfd3c86f2490e2033fee1c3647f4b01029ff047 Mon Sep 17 00:00:00 2001
From: mschuldt <mbschuldt@gmail.com>
Date: Tue, 18 Apr 2017 01:25:28 -0700
Subject: [PATCH] Non-recursive version of math-factorial-iter. Prevents error
"Variable binding depth exceeds max-specpdl-size"
---
lisp/calc/calc-comb.el | 12 +++++++-----
1 file changed, 7 insertions(+), 5 deletions(-)
diff --git a/lisp/calc/calc-comb.el b/lisp/calc/calc-comb.el
index c84ff23..a033d27 100644
--- a/lisp/calc/calc-comb.el
+++ b/lisp/calc/calc-comb.el
@@ -362,11 +362,13 @@
(math-gammap1-raw '(float -25 -2))))
(defun math-factorial-iter (count n f)
- (if (= (% n 5) 1)
- (math-working (format "factorial(%d)" (1- n)) f))
- (if (> count 0)
- (math-factorial-iter (1- count) (1+ n) (math-mul n f))
- f))
+ (while (> count 0)
+ (if (= (% n 5) 1)
+ (math-working (format "factorial(%d)" (1- n)) f))
+ (setq count (1- count)
+ f (math-mul n f)
+ n (1+ n)))
+ f)
(defun calcFunc-dfact (n) ; [I I] [F F] [Public]
(cond ((Math-integer-negp n)
--
2.7.4
^ permalink raw reply related [flat|nested] 2+ messages in thread
* Re: Fix for calculating large factorials
2017-04-18 8:44 Fix for calculating large factorials michael schuldt
@ 2017-04-18 18:28 ` Paul Eggert
0 siblings, 0 replies; 2+ messages in thread
From: Paul Eggert @ 2017-04-18 18:28 UTC (permalink / raw)
To: michael schuldt, emacs-devel
Thanks for the fix. I installed it here:
http://git.savannah.gnu.org/cgit/emacs.git/commit/?id=d831312d668fbedeffe3711b13cd455309da84a1
^ permalink raw reply [flat|nested] 2+ messages in thread
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