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authorRich Felker <dalias@aerifal.cx>2011-02-12 00:22:29 -0500
committerRich Felker <dalias@aerifal.cx>2011-02-12 00:22:29 -0500
commit0b44a0315b47dd8eced9f3b7f31580cf14bbfc01 (patch)
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initial check-in, version 0.5.0v0.5.0
Diffstat (limited to 'src/math/s_tanhf.c')
-rw-r--r--src/math/s_tanhf.c52
1 files changed, 52 insertions, 0 deletions
diff --git a/src/math/s_tanhf.c b/src/math/s_tanhf.c
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+/* 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;
+}