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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 power function
+//
+// DESCRIPTION:
+//
+// Raises complex A to the complex Zth power.
+// Definition is per AMS55 # 4.2.8,
+// analytically equivalent to cpow(a,z) = cexp(z clog(a)).
+//
+// ACCURACY:
+//
+// Relative error:
+// arithmetic domain # trials peak rms
+// IEEE -10,+10 30000 9.4e-15 1.5e-15
+
+// Pow returns x**y, the base-x exponential of y.
+// For generalized compatibility with math.Pow:
+//
+// Pow(0, ±0) returns 1+0i
+// Pow(0, c) for real(c)<0 returns Inf+0i if imag(c) is zero, otherwise Inf+Inf i.
+func Pow(x, y complex128) complex128 {
+ if x == 0 { // Guaranteed also true for x == -0.
+ if IsNaN(y) {
+ return NaN()
+ }
+ r, i := real(y), imag(y)
+ switch {
+ case r == 0:
+ return 1
+ case r < 0:
+ if i == 0 {
+ return complex(math.Inf(1), 0)
+ }
+ return Inf()
+ case r > 0:
+ return 0
+ }
+ panic("not reached")
+ }
+ modulus := Abs(x)
+ if modulus == 0 {
+ return complex(0, 0)
+ }
+ r := math.Pow(modulus, real(y))
+ arg := Phase(x)
+ theta := real(y) * arg
+ if imag(y) != 0 {
+ r *= math.Exp(-imag(y) * arg)
+ theta += imag(y) * math.Log(modulus)
+ }
+ s, c := math.Sincos(theta)
+ return complex(r*c, r*s)
+}