libgo/go/math/cmplx/exp.go

   1 // Copyright 2010 The Go Authors. All rights reserved.
   2 // Use of this source code is governed by a BSD-style
   3 // license that can be found in the LICENSE file.
   4
   5 package cmplx
   6
   7 import "math"
   8
   9 // The original C code, the long comment, and the constants
  10 // below are from http://netlib.sandia.gov/cephes/c9x-complex/clog.c.
  11 // The go code is a simplified version of the original C.
  12 //
  13 // Cephes Math Library Release 2.8:  June, 2000
  14 // Copyright 1984, 1987, 1989, 1992, 2000 by Stephen L. Moshier
  15 //
  16 // The readme file at http://netlib.sandia.gov/cephes/ says:
  17 //    Some software in this archive may be from the book _Methods and
  18 // Programs for Mathematical Functions_ (Prentice-Hall or Simon & Schuster
  19 // International, 1989) or from the Cephes Mathematical Library, a
  20 // commercial product. In either event, it is copyrighted by the author.
  21 // What you see here may be used freely but it comes with no support or
  22 // guarantee.
  23 //
  24 //   The two known misprints in the book are repaired here in the
  25 // source listings for the gamma function and the incomplete beta
  26 // integral.
  27 //
  28 //   Stephen L. Moshier
  29 //   moshier@na-net.ornl.gov
  30
  31 // Complex exponential function
  32 //
  33 // DESCRIPTION:
  34 //
  35 // Returns the complex exponential of the complex argument z.
  36 //
  37 // If
  38 //     z = x + iy,
  39 //     r = exp(x),
  40 // then
  41 //     w = r cos y + i r sin y.
  42 //
  43 // ACCURACY:
  44 //
  45 //                      Relative error:
  46 // arithmetic   domain     # trials      peak         rms
  47 //    DEC       -10,+10      8700       3.7e-17     1.1e-17
  48 //    IEEE      -10,+10     30000       3.0e-16     8.7e-17
  49
  50 // Exp returns e**x, the base-e exponential of x.
  51 func Exp(x complex128) complex128 {
  52         r := math.Exp(real(x))
  53         s, c := math.Sincos(imag(x))
  54         return complex(r*c, r*s)
  55 }