re PR libstdc++/10689 (pow(std::complex(0),1/3) returns (nan, nan) instead of 0.)

	PR libstdc++/10689
	* include/std/std_complex.h (pow): Tidy

From-SVN: r66989

libstdc++-v3/ChangeLog

+2003-05-20  Gabriel Dos Reis <gdr@integrable-solutions.net>
+
+	PR libstdc++/10689
+	* include/std/std_complex.h (pow): Tidy.
+	
 2003-05-19  Paolo Carlini  <pcarlini@unitus.it>
 
 	* testsuite/27_io/basic_filebuf/close/char/4.cc: New file, testing

libstdc++-v3/include/std/std_complex.h

@@ -565,24 +565,30 @@ namespace std
     }
 
   template<typename _Tp>
-    inline complex<_Tp>
+    complex<_Tp>
     pow(const complex<_Tp>& __x, const _Tp& __y)
     {
-      return exp(__y * log(__x));
+      if (__x.imag() == _Tp())
+        return pow(__x.real(), __y);
+
+      complex<_Tp> __t = log(__x);
+      return polar(exp(__y * __t.real()), __y * __t.imag());
     }
 
   template<typename _Tp>
     inline complex<_Tp>
     pow(const complex<_Tp>& __x, const complex<_Tp>& __y)
     {
-      return exp(__y * log(__x));
+      return __x == _Tp() ? _Tp() : exp(__y * log(__x));
     }
 
   template<typename _Tp>
     inline complex<_Tp>
     pow(const _Tp& __x, const complex<_Tp>& __y)
     {
-      return exp(__y * log(__x));
+      return __x == _Tp()
+        ? _Tp()
+        : polar(pow(__x, __y.real()), __y.imag() * log(__x));
     }
 
   // 26.2.3  complex specializations

libstdc++-v3/testsuite/26_numerics/complex/pow.C

+// PR libbstdc++/10689
+// Origin: Daniel.Levine@jhuaph.edu
+
+#include <complex>
+#include <testsuite_hooks.h>
+
+int main()
+{
+   std::complex<double> z(0, 1) ;
+
+   VERIFY(pow(z, 1.0/3.0) == 0.0);
+
+   return 0;
+}