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From: Edward Diener (eldiener_at_[hidden])
Date: 2021-04-08 02:22:07


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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