Re: does boost::variant support 128 bit integer?

From: Anil Muthigi (anilmuthigi123_at_[hidden])
Date: 2021-04-08 02:33:09

But I am not even doing any kind of input or output using __int128 FOR THE VARIANT VARIABLE….

As you can see… if you choose to use int instead of __int128 for the VARIANT VARIABLE and rerun the code…. it is actually printing the value of the __int128 variable d which I have used in the code..
 So, I guess it is actually picking up my std::ostream& operator<<(std::ostream& o, const __int128& x) functionality.

> On 08-Apr-2021, at 7:52 AM, Edward Diener via Boost-users <boost-users_at_[hidden]> wrote:
> 
> On 4/7/2021 9:58 PM, Edward Diener via Boost-users wrote:
>> On 4/7/2021 7:10 PM, Anil Muthigi via Boost-users wrote:
>>> If u see my code,  I have used __int128 separately for the variable d as well. If u change the variant variable' s data type from __int128 to int , it will run just fine.
>> The reason your code is failing is because your stream operator uses streaming and __int128 has no stream support. If you use an __int128 in a variant, but never use streaming, your code is fine. I do not know the reason why gcc and clang support __int128 but do not support the the type in streaming. Maybe you should try asking gcc about it or investigate it as a stackoverflow question.
>> Please do not topmost.
> 
> Apologies ! It looks as if the variant i/o is simply not picking up your std::ostream& operator<<(std::ostream& o, const __int128& x) functionality. I tried putting your functionality in namespace boost but it still did not pick it up.
> 
>>> 
>>> On Thu, 8 Apr 2021, 04:30 Edward Diener via Boost-users, <boost-users_at_[hidden] <mailto:boost-users_at_[hidden]>> wrote:
>>> 
>>>     On 4/7/2021 3:38 PM, Anil Muthigi via Boost-users wrote:
>>>      > I said that I am not sure if boost::variant supports __int128
>>>     because I
>>>      > had difficulties in compiling this code :
>>>      >
>>>      >  1.
>>>      >     #include <boost/variant.hpp>
>>>      >  2.
>>>      >     #include <string>
>>>      >  3.
>>>      >     #include <iostream>
>>>      >  4.
>>>      >     std::ostream& operator<<(std::ostream& o, const __int128& x)
>>>     { if (x
>>>      >     == std::numeric_limits<__int128>::min()) return o <<
>>>      >     "-170141183460469231731687303715884105728"; if (x < 0) return
>>>     o <<
>>>      >     "-" << -x; if (x < 10) return o << (char)(x + '0'); return o
>>>     << x /
>>>      >     10 << (char)(x % 10 + '0'); }
>>>      >  5.
>>>      >     int main()
>>>      >  6.
>>>      >     {
>>>      >  7.
>>>      >     boost::variant<__int128, char, std::string> v;
>>>      >  8.
>>>      >     v = 56;
>>>      >  9.
>>>      >     v = 'Y';
>>>      > 10.
>>>      >     __int128 d=12;
>>>      > 11.
>>>      >     std::cout <<d << '\n';
>>>      > 12.
>>>      >     std::cout << v << '\n';
>>>      > 13.
>>>      >     v = "Yashaswi raj";
>>>      > 14.
>>>      >     std::cout << v << '\n';
>>>      > 15.
>>>      >     }
>>>      >
>>>      > If u replace __int128 with int in the variant variable, it seems
>>>     to work
>>>      > just fine...
>>> 
>>>     My test with gcc-10.2 and clang-linux-11.0 shows that it does not
>>>     support __int128 in iostreams.
>>> 
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