From 8c656754aa2892cbd36968bfaab1ff7033edeb0f Mon Sep 17 00:00:00 2001
From: Christopher Swenson
Date: Mon, 27 Aug 2018 10:32:21 +1000
Subject: py/modmath: Add math.factorial, optimised and non-opt
 implementations.

This commit adds the math.factorial function in two variants:
- squared difference, which is faster than the naive version, relatively
  compact, and non-recursive;
- a mildly optimised recursive version, faster than the above one.

There are some more optimisations that could be done, but they tend to take
more code, and more storage space.  The recursive version seems like a
sensible compromise.

The new function is disabled by default, and uses the non-optimised version
by default if it is enabled.  The options are MICROPY_PY_MATH_FACTORIAL
and MICROPY_OPT_MATH_FACTORIAL.
---
 tests/float/math_factorial_intbig.py | 14 ++++++++++++++
 1 file changed, 14 insertions(+)
 create mode 100644 tests/float/math_factorial_intbig.py

(limited to 'tests/float')

diff --git a/tests/float/math_factorial_intbig.py b/tests/float/math_factorial_intbig.py
new file mode 100644
index 000000000..19d853df2
--- /dev/null
+++ b/tests/float/math_factorial_intbig.py
@@ -0,0 +1,14 @@
+try:
+    import math
+    math.factorial
+except (ImportError, AttributeError):
+    print('SKIP')
+    raise SystemExit
+
+
+for fun in (math.factorial,):
+    for x in range(-1, 30):
+        try:
+            print('%d' % fun(x))
+        except ValueError as e:
+            print('ValueError')
-- 
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