From 96223329d0b11a76e37a91b08a828571b5e97172 Mon Sep 17 00:00:00 2001
From: nobu <nobu@b2dd03c8-39d4-4d8f-98ff-823fe69b080e>
Date: Wed, 30 Aug 2017 07:55:19 +0000
Subject: array.c: refine descending_factorial

* array.c (descending_factorial): reduce factorial multipication.

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@59691 b2dd03c8-39d4-4d8f-98ff-823fe69b080e
---
 array.c | 14 ++++++++++----
 1 file changed, 10 insertions(+), 4 deletions(-)

(limited to 'array.c')

diff --git a/array.c b/array.c
index 674e354430..e131d1fc06 100644
--- a/array.c
+++ b/array.c
@@ -5079,10 +5079,16 @@ permute0(const long n, const long r, long *const p, char *const used, const VALU
 static VALUE
 descending_factorial(long from, long how_many)
 {
-    VALUE cnt = LONG2FIX(how_many >= 0);
-    while (how_many-- > 0) {
-	VALUE v = LONG2FIX(from--);
-	cnt = rb_int_mul(cnt, v);
+    VALUE cnt;
+    if (how_many > 0) {
+	cnt = LONG2FIX(from);
+	while (--how_many > 0) {
+	    long v = --from;
+	    cnt = rb_int_mul(cnt, LONG2FIX(v));
+	}
+    }
+    else {
+	cnt = LONG2FIX(how_many == 0);
     }
     return cnt;
 }
-- 
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