function-templates

问题 Scenario 1: a template function pred template<typename T> bool pred(T t) { /* return a bool based on t */ } Scenario 2: a set of functions overloaded on the same name pred bool pred(A t) { /* return a bool based on t */ } bool pred(B t) { /* return a bool based on t */ } bool pred(C t) { /* return a bool based on t */ } ... Whichever of the two scenarii we're in, the bottom line is that pred does not refer to a function, and so it cannot be passed around, e.g. as a unary predicate to std:

问题 I stumbled on this the other day and can't figure out which answer is correct, or whether both are acceptable. Specifically, I'm referring to the call to bar(T{}) in OtherFunction. From what I've been able to test on compiler explorer, the decision seems split. msvc and icc agree that it is ambiguous while gcc and clang compile the code without issue. The function bar inside the namespace hidden becomes visible through argument-dependent lookup. Additionally, msvc/icc consider the declaration

问题 This question already has answers here : using std::is_same, why my function still can't work for 2 types (4 answers) Closed 3 months ago . The compiler keeps assigning incompatible types during the build. error Message: error: assigning to 'int' from incompatible type 'QString' typeduserproperty.cpp:115:28: note: in instantiation of member function 'core::TypedUserProperty<int>::setValue' requested here Sample code /** * @brief setValue * set value to property * @param val * value to set to

问题 This question already has answers here : using std::is_same, why my function still can't work for 2 types (4 answers) Closed 3 months ago . The compiler keeps assigning incompatible types during the build. error Message: error: assigning to 'int' from incompatible type 'QString' typeduserproperty.cpp:115:28: note: in instantiation of member function 'core::TypedUserProperty<int>::setValue' requested here Sample code /** * @brief setValue * set value to property * @param val * value to set to

问题 This question already has answers here : using std::is_same, why my function still can't work for 2 types (4 answers) Closed 3 months ago . The compiler keeps assigning incompatible types during the build. error Message: error: assigning to 'int' from incompatible type 'QString' typeduserproperty.cpp:115:28: note: in instantiation of member function 'core::TypedUserProperty<int>::setValue' requested here Sample code /** * @brief setValue * set value to property * @param val * value to set to

问题 Supposedly std::abs is not constexpr in the standard (even in C++20). But in practice I found out that I can compile it as constexpr under the very peculiar condition that the function is templated. See this completely working example: template<class T> constexpr T f(const T input) { return std::abs(input); } int main() { int i = -1; int a = f(i); return 0; } The code: Compiles fine with GCC, with and without the template. It doesn't work in Clang. And in Visual Studio it compiles with the

来源： https://stackoverflow.com/questions/63896028/defining-a-single-template-for-a-member-function-within-a-class-template-with-bo

来源： https://stackoverflow.com/questions/63896028/defining-a-single-template-for-a-member-function-within-a-class-template-with-bo

问题 I have some classes which can be checked. The code which implements this declares a function template in a header file and specializes it in different source files: // check.h template <class T> bool check(const T& object); // class1.h struct Class1 {int mass;}; // check_class1.cpp #include "class1.h" #include "check.h" template <> bool check(const Class1& object) {return object.mass < 100;} // class2.h struct Class2 {int price;}; // check_class2.cpp #include "class2.h" #include "check.h"

问题 [temp.arg.explicit]/3 of the C++17 standard (final draft) says about deduction of function template arguments with explicitly specified template argument lists: In contexts where deduction is done and fails, or [...], if a template argument list is specified and it, along with any default template arguments, identifies a single function template specialization, then the template-id is an lvalue for the function template specialization. How does this apply to parameter packs? Consider template