From 4483d59fbdb9f62ec7ddff9c1acc8af907fca72f Mon Sep 17 00:00:00 2001
From: nobu <nobu@b2dd03c8-39d4-4d8f-98ff-823fe69b080e>
Date: Tue, 2 Aug 2016 12:42:42 +0000
Subject: math.c: faster tanh

* math.c (tanh): make faster by the extract form if three
  hyperbolic functions are unavailable.  [Feature #12647]

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@55799 b2dd03c8-39d4-4d8f-98ff-823fe69b080e
---
 math.c | 5 +++++
 1 file changed, 5 insertions(+)

(limited to 'math.c')

diff --git a/math.c b/math.c
index eefcec3c93..b15e87113c 100644
--- a/math.c
+++ b/math.c
@@ -283,8 +283,13 @@ math_sinh(VALUE obj, VALUE x)
 double
 tanh(double x)
 {
+# if defined(HAVE_SINH) && defined(HAVE_COSH)
     const double c = cosh(x);
     if (!isinf(c)) return sinh(x) / c;
+# else
+    const double e = exp(x+x);
+    if (!isinf(e)) return (e - 1) / (e + 1);
+# endif
     return x > 0 ? 1.0 : -1.0;
 }
 #endif
-- 
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