https://gcc.gnu.org/bugzilla/show_bug.cgi?id=90638
--- Comment #7 from Igor Smirnov <Igor.Smirnov at cern dot ch> ---
There can be still problems with big integer powers of complex numbers in the
latest versions.
I just don't see a single correct answer.
As above the expected correct responses are marked by "should be" and the
received by "actually".
Notations of version started from "C++" are from the above mentioned site:
---------------------------------------------------------------
#include <iostream>
#include <complex>
#include <limits.h>
int main(void)
{
double phi = M_PI / LONG_MAX;
std::cout<<phi<<'\n';
// Should be 3.40612e-19
std::complex< double > var0 = std::polar(1.0, phi);
std::cout<<var0 << '\n';
// Should be (1,3.40612e-19)
long lp1 = LONG_MAX;
unsigned long lp2 = (unsigned long)lp1+1;
std::cout<<lp1<<' '<<lp2<<'\n';
// Should be 2147483647 2147483648
std::cout<<' '<<pow(var0, lp1)
<<' '<<pow(var0, lp2)
<<'\n'<<'\n';
// Should be (-1, zero or very small number) (-1,-3.40612e-19)
// Actually (1,-3.40612e-19) (1,0) by 4.8.5
// (-1,1.22465e-16) (-1,1.22465e-16) by C++ 10.0.0.1
// (1,-3.40612e-19) (1,0) by C++03 10.0.0.1
// (1,-3.40612e-19) (1,0) by C++03(GNU) 10.0.0.1
// (-1,1.22465e-16) (-1,1.22465e-16) by C++11 10.0.0.1
// (-1,1.22465e-16) (-1,1.22465e-16) by C++11(GNU) 10.0.0.1
// (-1,1.22465e-16) (-1,1.22465e-16) by C++ 14 10.0.0.1
// (-1,1.22465e-16) (-1,1.22465e-16) by C++ 14(GNU) 10.0.0.1
// (-1,1.22465e-16) (-1,1.22465e-16) by C++ 17 10.0.0.1
// (-1,1.22465e-16) (-1,1.22465e-16) by C++17(GNU) 10.0.0.1
// (-1,1.22465e-16) (-1,1.22465e-16) by C++2a 10.0.0.1
// (-1,1.22465e-16) (-1,1.22465e-16) by C++2a(GNU) 10.0.0.1
long double phid = M_PI / LONG_MAX;
std::cout<<phid<<'\n';
// Should be 3.40612e-19
std::complex< long double > vard0 = std::polar((long double)1.0, phid);
std::cout<<vard0 << '\n';
// Should be (1,3.40612e-19)
std::cout<<' '<<pow(vard0, lp1)
<<' '<<pow(vard0, lp2)
<<'\n'<<'\n';
// Should be (-1, zero or very small number) (-1,-3.40612e-19)
// Actually (1,-3.40612e-19) (1,0) at 4.8.5
// (-1,1.22898e-16) (-1,1.22465e-16) by C++ 10.0.0.1
// (1,-3.40612e-19) (1,0) by C++03 10.0.0.1
// (1,-3.40612e-19) (1,0) C++03(GNU) 10.0.0.1
// etc.
// (-1,1.22898e-16) (-1,1.22465e-16) by C++ 17 10.0.0.1
// (-1,1.22898e-16) (-1,1.22465e-16) by C++17(GNU) 10.0.0.1
// (-1,1.22898e-16) (-1,1.22465e-16) by C++2a(GNU) 10.0.0.1
double phi1 = M_PI / ULONG_MAX;
std::cout<<phi1<<'\n';
// Should be 1.70306e-19
std::complex< double > var1 = std::polar(1.0, phi1);
std::cout<<var1 <<'\n';
// Should be (1,1.70306e-19)
unsigned long lp3 = ULONG_MAX;
std::cout<<lp3<<'\n';
// Should be 18446744073709551615
std::cout<<' '<<pow(var1, lp3)
<<'\n'<<'\n';
// Should be (-1, zero or very small number)
// Actually (1,-1.70306e-19) by 4.8.5
// (-1,1.22465e-16) by C++ 10.0.0.1
// (1,-1.70306e-19) by C++03 10.0.0.1
// etc.
// (-1,1.22465e-16) by C++ 17 10.0.0.1
}
-------------------------------------------------------------
Example of the output by 4.8.5:
3.40612e-19
(1,3.40612e-19)
9223372036854775807 9223372036854775808
(1,-3.40612e-19) (1,0)
3.40612e-19
(1,3.40612e-19)
(1,-3.40612e-19) (1,0)
1.70306e-19
(1,1.70306e-19)
18446744073709551615
(1,-1.70306e-19)
Other versions are in comments.
