C++: Print representation of double in hex

Question

Is there a simple way to manipulate std::cout so that it prints doubles in their hex representation? In other words, something equivalent to:

printf("%" PRIx64, *reinterpret_cast<uint64_t *>(&my_double));

To provide some context, I have a program which prints hundreds of floating-point results and I was wondering if there is that magical one-line hack that can print all of them in hex.

Sheerlegs

https://mcmap.net/q/17201/-c-cout-hex-values – Matroclinous

Answer 1

Take a look at std::hexfloat if you can use C++11

Example:

double k = 3.14;
std::cout<< std::hexfloat << k << std::endl;

prints: 0x1.91eb85p+1

Hf

Damn, exactly what I needed but g++ does not support it yet. – Sheerlegs

Note that this doesn't do the same thing as your printf thing (which is also illegal, anyway). – Grapeshot

Wasn't gcc supposed to be fully C++11 compliant? – Hf

Not yet according to this gcc.gnu.org/onlinedocs/libstdc++/manual/status.html – Sheerlegs

@Grapeshot Why is my printf illegal? – Sheerlegs

It breakes strict aliasing rules. – Grapeshot

It's funny how gcc/clang/icc don't have hexfloat but MSVC does – Hf

The big surprise from MS! :P – Sheerlegs

@Sheerlegs memcpy from double to uint64_t or ORing bytes together manualy. – Grapeshot

Answer 2

You can use this

    #include <iomanip> //Include this file
    cout<<hex<<*reinterpret_cast<unsigned __int64 *>(&r);

Critchfield

Answer 3

You can get std::cout to print in hex with:

std::cout << std::hex << num

Spatula