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/*
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/*
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 *  Mathlib : A C Library of Special Functions
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 *  Mathlib : A C Library of Special Functions
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 *  Copyright (C) 2013-2016 The R Core Team
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 *  Copyright (C) 2013-2022 The R Core Team
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 *
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 *
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 *  This program is free software; you can redistribute it and/or modify
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 *  This program is free software; you can redistribute it and/or modify
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 *  it under the terms of the GNU General Public License as published by
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 *  it under the terms of the GNU General Public License as published by
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 *  the Free Software Foundation; either version 2 of the License, or
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 *  the Free Software Foundation; either version 2 of the License, or
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 *  (at your option) any later version.
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 *  (at your option) any later version.
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    // otherwise
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    // otherwise
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    return sin(M_PI * x);
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    return sin(M_PI * x);
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}
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}
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#endif
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#endif
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// tan(pi * x)  -- exact when x = k/2  for all integer k
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// tan(pi * x)  -- exact when x = k/4  for all integer k and half-values give NaN
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#if defined(HAVE_TANPI) || defined(HAVE___TANPI)
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// for use in arithmetic.c, half-values documented to give NaN
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// ----------- e.g. used in ../main/arithmetic.c :
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double Rtanpi(double x)
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double Rtanpi(double x)
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#else
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double tanpi(double x)
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#endif
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{
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{
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#ifdef IEEE_754
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#ifdef IEEE_754
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    if (ISNAN(x)) return x;
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    if (ISNAN(x)) return x;
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#endif
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#endif
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    if(!R_FINITE(x)) ML_WARN_return_NAN;
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    if(!R_FINITE(x)) ML_WARN_return_NAN;
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    x = fmod(x, 1.); // tan(pi(x + k)) == tan(pi x)  for all integer k
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    x = fmod(x, 1.); // tan(pi(x + k)) == tan(pi x)  for all integer k
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    // map (-1,1) --> (-1/2, 1/2] :
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    // map (-1,1] --> (-1/2, 1/2] :
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    if(x <= -0.5) x++; else if(x > 0.5) x--;
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    if(x <= -0.5) x++; else if(x > 0.5) x--;
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    return (x == 0.) ? 0. : ((x == 0.5) ? ML_NAN : tan(M_PI * x));
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    return (x == 0.) ? 0. :
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	((x ==  0.5 ) ? ML_NAN :
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	((x ==  0.25) ?  1. :
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	((x == -0.25) ? -1. :
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			tan(M_PI * x)
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	    )));
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}
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}
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#if defined(HAVE_TANPI) || defined(HAVE___TANPI)
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#else
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double tanpi(double x) {
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    return Rtanpi(x);
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}
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#endif
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#if !defined(HAVE_TANPI) && defined(HAVE___TANPI)
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#if !defined(HAVE_TANPI) && defined(HAVE___TANPI)
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double tanpi(double x) {
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double tanpi(double x) {
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    return __tanpi(x);
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    return __tanpi(x);
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}
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}
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/* #else tanpi() defined from C standard math lib */
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#endif
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#endif