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Diffstat (limited to 'src/pkg/math/tan.go')
| -rw-r--r-- | src/pkg/math/tan.go | 130 |
1 files changed, 0 insertions, 130 deletions
diff --git a/src/pkg/math/tan.go b/src/pkg/math/tan.go deleted file mode 100644 index 285eff1ab..000000000 --- a/src/pkg/math/tan.go +++ /dev/null @@ -1,130 +0,0 @@ -// 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 Tan(x float64) float64 - -func tan(x float64) float64 { - const ( - PI4A = 7.85398125648498535156E-1 // 0x3fe921fb40000000, Pi/4 split into three parts - PI4B = 3.77489470793079817668E-8 // 0x3e64442d00000000, - PI4C = 2.69515142907905952645E-15 // 0x3ce8469898cc5170, - M4PI = 1.273239544735162542821171882678754627704620361328125 // 4/pi - ) - // special cases - switch { - case x == 0 || IsNaN(x): - return x // return ±0 || NaN() - case IsInf(x, 0): - return NaN() - } - - // make argument positive but save the sign - sign := false - if x < 0 { - x = -x - sign = true - } - - j := int64(x * M4PI) // integer part of x/(Pi/4), as integer for tests on the phase angle - y := float64(j) // integer part of x/(Pi/4), as float - - /* map zeros and singularities to origin */ - if j&1 == 1 { - j += 1 - y += 1 - } - - z := ((x - y*PI4A) - y*PI4B) - y*PI4C - zz := z * z - - if zz > 1e-14 { - y = z + z*(zz*(((_tanP[0]*zz)+_tanP[1])*zz+_tanP[2])/((((zz+_tanQ[1])*zz+_tanQ[2])*zz+_tanQ[3])*zz+_tanQ[4])) - } else { - y = z - } - if j&2 == 2 { - y = -1 / y - } - if sign { - y = -y - } - return y -} |