From ad9f2fdca4e2860117d3f5e574a66d428ade8ddf Mon Sep 17 00:00:00 2001
From: HybridDog <ovvv@web.de>
Date: Tue, 5 Mar 2019 10:11:21 +0100
Subject: [PATCH] Add math.factorial (#8298)

---
 builtin/common/misc_helpers.lua | 14 ++++++++++++++
 1 file changed, 14 insertions(+)

diff --git a/builtin/common/misc_helpers.lua b/builtin/common/misc_helpers.lua
index 16c497156..e8912e57a 100644
--- a/builtin/common/misc_helpers.lua
+++ b/builtin/common/misc_helpers.lua
@@ -243,6 +243,20 @@ function math.sign(x, tolerance)
 	return 0
 end
 
+--------------------------------------------------------------------------------
+function math.factorial(x)
+	assert(x % 1 == 0 and x >= 0, "factorial expects a non-negative integer")
+	if x >= 171 then
+		-- 171! is greater than the biggest double, no need to calculate
+		return math.huge
+	end
+	local v = 1
+	for k = 2, x do
+		v = v * k
+	end
+	return v
+end
+
 --------------------------------------------------------------------------------
 function get_last_folder(text,count)
 	local parts = text:split(DIR_DELIM)