Defined in header <functional> | ||
---|---|---|
template<> class plus<void>; | (since C++14) |
std::plus<>
is a specialization of std::plus
with parameter and return type deduced.
Member type | Definition |
---|---|
is_transparent | /* unspecified */ |
operator() | returns the sum of two arguments (public member function) |
template< class T, class U> constexpr auto operator()( T&& lhs, U&& rhs ) const -> decltype(std::forward<T>(lhs) + std::forward<U>(rhs)); |
Returns the sum of lhs
and rhs
.
lhs, rhs | - | values to sum |
The result of lhs + rhs
.
The member type is_transparent
indicates to the caller that this function object is a transparent function object: it accepts arguments of arbitrary types and uses perfect forwarding, which avoids unnecessary copying and conversion when the function object is used in heterogeneous context, or with rvalue arguments. In particular, template functions such as std::set::find
and std::set::lower_bound
make use of this member type on their Compare
types.
#include <functional> #include <iostream> int main() { std::string a = "Hello "; const char* b = "world"; std::cout << std::plus<>{}(a, b) << '\n'; }
Output:
Hello world
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