#include <chrono>
namespace X
{
using namespace std;
struct A
{
std::chrono::seconds d = 0s; // ok
};
}
namespace Y
{
struct B
{
std::chrono::seconds d = 0s; // error
};
}
The error message is:
error : no matching literal operator for call to 'operator""s' with argument of type 'unsigned long long' or 'const char *', and no matching literal operator template std::chrono::seconds d = 0s;
My question is:
I don't want to use namespace std;
in namespace Y
; then, how should I make std::operator""s
visible in namespace Y
?
If you want to have all the chrono literals then you can use
using namespace std::chrono_literals;
If you just want operator""s
then you can use
using std::chrono_literals::operator""s;
Do note that at least on coliru gcc issues a warning for the above line but clang does not. To me there should be no warning. I have asked a follow up question about this at Should a using command issue a warning when using a reserved identifier?
tl;dr: Use
using namespace std::string_literals
These operators are declared in the namespace
std::literals::string_literals
, where bothliterals
andstring_literals
are inline namespaces. Access to these operators can be gained withusing namespace std::literals
,using namespace std::string_literals
, andusing namespace std::literals::string_literals
.
Source: https://en.cppreference.com/w/cpp/string/basic_string/operator%22%22s
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