You can create a macro like #define FUNCTORIZE(func) [](auto&&… val) \ noexcept(noexcept(func(std::forward<decltype(val)>(val)…))) -> decltype(auto) \ {return func(std::forward<decltype(val)>(val)…);} which will let you wrap any callable into a closure object. You would use it like auto constexpr predObj = FUNCTORIZE(pred);
The unspecialized function templates are also called the underlying base templates. Base templates can be specialized. The overloading rules to see which ones get called in different situations, are pretty simple, at least at a high level: Nontemplate functions are first-class citizens. A plain old nontemplate function that matches the parameter types as well as … Read more
So to start with, the first expression can only possibly call the first overload. It is not a valid expression for a Func<Task> because there is a code path that returns an invalid value (void instead of Task). () => while(true) is actually a valid method for either signature. (It, along with implementations such as … Read more
It’s obvious to us which function you intend to be chosen, but the compiler has to follow the rules of C++ not use clever leaps of logic (or even not so clever ones, as in simple cases like this!) The relevant constructor of std::function is: template<class F> function(F f); which is a template that accepts … Read more
Looks like a Clang bug to me. The general rule is that member functions of the same name in different base classes do not overload. For example: struct Foo { void bar(); }; struct Baz { void bar(int); }; struct Quux : Foo, Baz { }; int main() { Quux().bar(); } // error on both … Read more
The answer is in the C# specification section 7.3 and section 7.5.5.1 I broke down the steps used for choosing the method to invoke. First, the set of all accessible members named N (N=Foo) declared in T (T=class D) and the base types of T (class C) is constructed. Declarations that include an override modifier … Read more
There is a huge problem with argument-dependent lookup. Consider, for example, the following utility: #include <iostream> namespace utility { template <typename T> void print(T x) { std::cout << x << std::endl; } template <typename T> void print_n(T x, unsigned n) { for (unsigned i = 0; i < n; ++i) print(x); } } It’s simple … Read more
“Hello World” is a string literal of type “array of 12 const char” which can be converted to a “pointer to const char” which can in turn be converted to a bool. That’s precisely what is happening. The compiler prefers this to using std::string‘s conversion constructor. A conversion sequence involving a conversion constructor is known … Read more
The fundamental reason for this (standard-conforming) ambiguity appears to lie within the cost of conversion: Overload resolution tries to minimize the operations performed to convert an argument to the corresponding parameter. An array is effectively the pointer to its first element though, decorated with some compile-time type information. An array-to-pointer conversion doesn’t cost more than … Read more
For the exact rules, see the overload resolution spec. But briefly, it goes like this. First, make a list of all the accessible constructors. public EffectOptions ( params object [ ] options ) public EffectOptions ( IEnumerable<object> options ) public EffectOptions ( string name ) public EffectOptions ( object owner ) public EffectOptions ( int … Read more