1 files changed, 52 insertions, 0 deletions
diff --git a/src/math/s_tanhf.c b/src/math/s_tanhf.c
new file mode 100644
index 00000000..a0820409
--- /dev/null
+++ b/src/math/s_tanhf.c
@@ -0,0 +1,52 @@
+/* s_tanhf.c -- float version of s_tanh.c.
+ * Conversion to float by Ian Lance Taylor, Cygnus Support, ian@cygnus.com.
+ */
+
+/*
+ * ====================================================
+ * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
+ *
+ * Developed at SunPro, a Sun Microsystems, Inc. business.
+ * Permission to use, copy, modify, and distribute this
+ * software is freely granted, provided that this notice
+ * is preserved.
+ * ====================================================
+ */
+
+#include <math.h>
+#include "math_private.h"
+
+static const float one=1.0, two=2.0, tiny = 1.0e-30;
+
+float
+tanhf(float x)
+{
+        float t,z;
+        int32_t jx,ix;
+
+        GET_FLOAT_WORD(jx,x);
+        ix = jx&0x7fffffff;
+
+    /* x is INF or NaN */
+        if(ix>=0x7f800000) {
+            if (jx>=0) return one/x+one;    /* tanh(+-inf)=+-1 */
+            else       return one/x-one;    /* tanh(NaN) = NaN */
+        }
+
+    /* |x| < 22 */
+        if (ix < 0x41b00000) {          /* |x|<22 */
+            if (ix<0x24000000)          /* |x|<2**-55 */
+                return x*(one+x);       /* tanh(small) = small */
+            if (ix>=0x3f800000) {       /* |x|>=1  */
+                t = expm1f(two*fabsf(x));
+                z = one - two/(t+two);
+            } else {
+                t = expm1f(-two*fabsf(x));
+                z= -t/(t+two);
+            }
+    /* |x| > 22, return +-1 */
+        } else {
+            z = one - tiny;             /* raised inexact flag */
+        }
+        return (jx>=0)? z: -z;
+}