````// Copyright 2010 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 cmplx`

`import "math"`

`// The original C code, the long comment, and the constants`
`// below are from http://netlib.sandia.gov/cephes/c9x-complex/clog.c.`
`// The go code is a simplified version of the original C.`
`//`
`// 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`

`// Complex exponential function`
`//`
`// DESCRIPTION:`
`//`
`// Returns the complex exponential of the complex argument z.`
`//`
`// If`
`//     z = x + iy,`
`//     r = exp(x),`
`// then`
`//     w = r cos y + i r sin y.`
`//`
`// ACCURACY:`
`//`
`//                      Relative error:`
`// arithmetic   domain     # trials      peak         rms`
`//    DEC       -10,+10      8700       3.7e-17     1.1e-17`
`//    IEEE      -10,+10     30000       3.0e-16     8.7e-17`

`// Exp returns e**x, the base-e exponential of x.`
`func Exp(x complex128) complex128 {`
`	switch re, im := real(x), imag(x); {`
`	case math.IsInf(re, 0):`
`		switch {`
`		case re > 0 && im == 0:`
`			return x`
`		case math.IsInf(im, 0) || math.IsNaN(im):`
`			if re < 0 {`
`				return complex(0, math.Copysign(0, im))`
`			} else {`
`				return complex(math.Inf(1.0), math.NaN())`
`			}`
`		}`
`	case math.IsNaN(re):`
`		if im == 0 {`
`			return complex(math.NaN(), im)`
`		}`
`	}`
`	r := math.Exp(real(x))`
`	s, c := math.Sincos(imag(x))`
`	return complex(r*c, r*s)`
`}`
```