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+// 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)
+}