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/* @(#)s_tanh.c 5.1 93/09/24 */ |
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/* @(#)s_tanh.c 5.1 93/09/24 */ |
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/* |
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/* |
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* ==================================================== |
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* ==================================================== |
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* Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved. |
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* Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved. |
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* |
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* |
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* Developed at SunPro, a Sun Microsystems, Inc. business. |
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* software is freely granted, provided that this notice |
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* is preserved. |
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* is preserved. |
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* ==================================================== |
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* ==================================================== |
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*/ |
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*/ |
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/* |
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FUNCTION |
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<>, <>---hyperbolic tangent |
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INDEX |
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tanh |
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INDEX |
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tanhf |
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ANSI_SYNOPSIS |
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#include |
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double tanh(double <[x]>); |
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float tanhf(float <[x]>); |
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TRAD_SYNOPSIS |
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#include |
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double tanh(<[x]>) |
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double <[x]>; |
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float tanhf(<[x]>) |
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float <[x]>; |
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DESCRIPTION |
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<> computes the hyperbolic tangent of |
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the argument <[x]>. Angles are specified in radians. |
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<)>> is defined as |
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. sinh(<[x]>)/cosh(<[x]>) |
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<> is identical, save that it takes and returns <> values. |
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RETURNS |
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The hyperbolic tangent of <[x]> is returned. |
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PORTABILITY |
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<> is ANSI C. <> is an extension. |
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*/ |
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/* Tanh(x) |
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/* Tanh(x) |
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* Return the Hyperbolic Tangent of x |
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* Return the Hyperbolic Tangent of x |
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* |
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* Special cases: |
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* tanh(NaN) is NaN; |
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* tanh(NaN) is NaN; |
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* only tanh(0)=0 is exact for finite argument. |
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* only tanh(0)=0 is exact for finite argument. |
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*/ |
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*/ |
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#include |
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#include "fdlibm.h" |
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#ifndef _DOUBLE_IS_32BITS |
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#include "fdlibm.h" |
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#ifdef __STDC__ |
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#ifdef __STDC__ |
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static const double one=1.0, two=2.0, tiny = 1.0e-300; |
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static const double one=1.0, two=2.0, tiny = 1.0e-300; |
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#else |
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#else |
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static double one=1.0, two=2.0, tiny = 1.0e-300; |
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#endif |
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static double one=1.0, two=2.0, tiny = 1.0e-300; |
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#ifdef __STDC__ |
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double tanh(double x) |
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#else |
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double tanh(x) |
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#endif |
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double x; |
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#endif |
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double tanh(double x) |
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{ |
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{ |
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double t,z; |
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double t,z; |
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__int32_t jx,ix; |
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int jx,ix,lx; |
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/* High word of |x|. */ |
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/* High word of |x|. */ |
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GET_HIGH_WORD(jx,x); |
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EXTRACT_WORDS(jx,lx,x); |
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ix = jx&0x7fffffff; |
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ix = jx&0x7fffffff; |
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/* x is INF or NaN */ |
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/* x is INF or NaN */ |
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if(ix>=0x7ff00000) { |
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if(ix>=0x7ff00000) { |
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if (jx>=0) return one/x+one; /* tanh(+-inf)=+-1 */ |
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if (jx>=0) return one/x+one; /* tanh(+-inf)=+-1 */ |
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else return one/x-one; /* tanh(NaN) = NaN */ |
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} |
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else return one/x-one; /* tanh(NaN) = NaN */ |
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} |
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/* |x| < 22 */ |
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if (ix < 0x40360000) { /* |x|<22 */ |
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/* |x| < 22 */ |
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if ((ix | lx) == 0) |
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if (ix < 0x40360000) { /* |x|<22 */ |
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return x; /* x == +-0 */ |
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if (ix<0x3c800000) /* |x|<2**-55 */ |
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if (ix<0x3c800000) /* |x|<2**-55 */ |
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return x*(one+x); /* tanh(small) = small */ |
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return x*(one+x); /* tanh(small) = small */ |
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if (ix>=0x3ff00000) { /* |x|>=1 */ |
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if (ix>=0x3ff00000) { /* |x|>=1 */ |
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t = expm1(two*fabs(x)); |
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t = __expm1(two*fabs(x)); |
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z = one - two/(t+two); |
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z = one - two/(t+two); |
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} else { |
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} else { |
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t = expm1(-two*fabs(x)); |
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t = __expm1(-two*fabs(x)); |
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z= -t/(t+two); |
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z= -t/(t+two); |
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} |
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} |
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/* |x| > 22, return +-1 */ |
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} else { |
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z = one - tiny; /* raised inexact flag */ |