Q. about GDR's addition of complex-accessor overloads.

[Jan van Dijk]

	L.S,

With patch http://gcc.gnu.org/ml/gcc-patches/2004-01/msg00866.html Gabriel Dos 
Reis changed the real() and imag() members of std::complex<T>. These were 
changed to return const references, while non-const overloads were added to 
return unqualified references.

This causes problem with the following (reduced) program:

#include <complex>
#include <functional>

typedef std::complex<double> complex;

void foo()
{
        std::mem_fun_ref(&complex::real);
}

which gives me, with today's trunk:

./cmplx_acc_overload.cpp: In function ‘void foo()’:
./cmplx_acc_overload.cpp:10: error: call of overloaded 
‘mem_fun_ref(<unresolved overloaded function type>)’ is ambiguous
/home/jan/local/gcc-head/lib/gcc/i686-pc-linux-gnu/4.1.0/../../../../include/c++/4.1.0/bits/stl_function.h:723: 
note: candidates are: std::mem_fun_ref_t<_Ret, _Tp> std::mem_fun_ref(_Ret 
(_Tp::*)()) [with _Ret = double&, _Tp = std::complex<double>]
/home/jan/local/gcc-head/lib/gcc/i686-pc-linux-gnu/4.1.0/../../../../include/c++/4.1.0/bits/stl_function.h:728: 
note:                 std::const_mem_fun_ref_t<_Ret, _Tp> 
std::mem_fun_ref(_Ret (_Tp::*)()const) [with _Ret = const double&, _Tp = 
std::complex<double>]

Translated to English this means: should I create a const_mem_fun_ref_t with 
complex::real() const, or a a mem_fun_ref_t with the non-const real() 
overload?

Since the standard (26.2.2, or more particular: 26.2.3) mentions only one 
real() and imag(), it is my belief that the above test program is correct, 
and gcc's libstdc++ is off-specs.

Any thoughts?

In case this issue has already been discussed, I apologize for not googling 
well enough and a pointer to the previous discourse would be appreciated.

With kind regards,

	Jan van Dijk

-- 
dr. Jan van Dijk
Department of Applied Physics
Group Elementary Processes in Gas Discharges
Eindhoven University of Technology
The Netherlands
jan@etpmod.phys.tue.nl
+31 40 247 57 65