// Copyright 2011 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.

package math

/*
	Floating-point tangent.
*/

// The original C code, the long comment, and the constants
// below were from http://netlib.sandia.gov/cephes/cmath/sin.c,
// available from http://www.netlib.org/cephes/cmath.tgz.
// The go code is a simplified version of the original C.
//
//      tan.c
//
//      Circular tangent
//
// SYNOPSIS:
//
// double x, y, tan();
// y = tan( x );
//
// DESCRIPTION:
//
// Returns the circular tangent of the radian argument x.
//
// Range reduction is modulo pi/4.  A rational function
//       x + x**3 P(x**2)/Q(x**2)
// is employed in the basic interval [0, pi/4].
//
// ACCURACY:
//                      Relative error:
// arithmetic   domain     # trials      peak         rms
//    DEC      +-1.07e9      44000      4.1e-17     1.0e-17
//    IEEE     +-1.07e9      30000      2.9e-16     8.1e-17
//
// Partial loss of accuracy begins to occur at x = 2**30 = 1.074e9.  The loss
// is not gradual, but jumps suddenly to about 1 part in 10e7.  Results may
// be meaningless for x > 2**49 = 5.6e14.
// [Accuracy loss statement from sin.go comments.]
//
// Cephes Math Library Release 2.8:  June, 2000
// Copyright 1984, 1987, 1989, 1992, 2000 by Stephen L. Moshier
//
// The readme file at http://netlib.sandia.gov/cephes/ says:
//    Some software in this archive may be from the book _Methods and
// Programs for Mathematical Functions_ (Prentice-Hall or Simon & Schuster
// International, 1989) or from the Cephes Mathematical Library, a
// commercial product. In either event, it is copyrighted by the author.
// What you see here may be used freely but it comes with no support or
// guarantee.
//
//   The two known misprints in the book are repaired here in the
// source listings for the gamma function and the incomplete beta
// integral.
//
//   Stephen L. Moshier
//   moshier@na-net.ornl.gov

// tan coefficients
var _tanP = [...]float64{
	-1.30936939181383777646e4, // 0xc0c992d8d24f3f38
	1.15351664838587416140e6,  // 0x413199eca5fc9ddd
	-1.79565251976484877988e7, // 0xc1711fead3299176
}
var _tanQ = [...]float64{
	1.00000000000000000000e0,
	1.36812963470692954678e4,  // 0x40cab8a5eeb36572
	-1.32089234440210967447e6, // 0xc13427bc582abc96
	2.50083801823357915839e7,  // 0x4177d98fc2ead8ef
	-5.38695755929454629881e7, // 0xc189afe03cbe5a31
}

// Tan returns the tangent of the radian argument x.
//
// Special cases are:
//
//	Tan(±0) = ±0
//	Tan(±Inf) = NaN
//	Tan(NaN) = NaN
func ( float64) float64 {
	if haveArchTan {
		return archTan()
	}
	return tan()
}

func ( float64) float64 {
	const (
		 = 7.85398125648498535156e-1  // 0x3fe921fb40000000, Pi/4 split into three parts
		 = 3.77489470793079817668e-8  // 0x3e64442d00000000,
		 = 2.69515142907905952645e-15 // 0x3ce8469898cc5170,
	)
	// special cases
	switch {
	case  == 0 || IsNaN():
		return  // return ±0 || NaN()
	case IsInf(, 0):
		return NaN()
	}

	// make argument positive but save the sign
	 := false
	if  < 0 {
		 = -
		 = true
	}
	var  uint64
	var ,  float64
	if  >= reduceThreshold {
		,  = trigReduce()
	} else {
		 = uint64( * (4 / Pi)) // integer part of x/(Pi/4), as integer for tests on the phase angle
		 = float64()           // integer part of x/(Pi/4), as float

		/* map zeros and singularities to origin */
		if &1 == 1 {
			++
			++
		}

		 = (( - *) - *) - *
	}
	 :=  * 

	if  > 1e-14 {
		 =  + *(*(((_tanP[0]*)+_tanP[1])*+_tanP[2])/((((+_tanQ[1])*+_tanQ[2])*+_tanQ[3])*+_tanQ[4]))
	} else {
		 = 
	}
	if &2 == 2 {
		 = -1 / 
	}
	if  {
		 = -
	}
	return 
}