Yes. The same reason if you only ever read an argument you make the parameter const&. T // I’m copying this T& // I’m modifying this const T& // I’m reading this Those are your “defaults”. When T is a fundamental type (built-in), though, you generally just revert to const T (no reference) for reading, … Read more
C++20 allows auto as function parameter type This code is valid using C++20: int function(auto data) { // do something, there is no constraint on data } As an abbreviated function template. This is a special case of a non constraining type-constraint (i.e. unconstrained auto parameter). Using concepts, the constraining type-constraint version (i.e. constrained auto … Read more
A constraint on the deduced auto type doesn’t mean it needs to be a specific type, it means it needs to be one of a set of types that satisfy the constraint. Note that a constraint and a type are not the same thing, and they’re not interchangeable. e.g. a concept like std::integral constrains the … Read more
The template <auto> feature (P0127R1) was accepted into C++ in the ISO C++ 2016 meeting in Oulu, Finland. An auto keyword in a template parameter can be used to indicate a non-type parameter the type of which is deduced at the point of instantiation. It helps to think of this as a more convenient way … Read more
C++14 has this feature. You can test it with new versions of GCC or clang by setting the -std=c++1y flag. Live example In addition to that, in C++14 you can also use decltype(auto) (which mirrors decltype(auto) as that of variables) for your function to deduce its return value using decltype semantics. An example would be … Read more
Dropping the explicit auto would break the language: e.g. int main() { int n; { auto n = 0; // this shadows the outer n. } } where you can see that dropping the auto would not shadow the outer n.
I like to use idea from Effective Modern C++ which uses non-implemented template; the type is output with compiler error: template<typename T> struct TD; Now for auto variable var, after its definition add: TD<decltype(var)> td; And watch error message for your compiler, it will contain type of var.
Read this article: Appearing and Disappearing consts in C++ Type deduction for auto variables in C++0x is essentially the same as for template parameters. (As far as I know, the only difference between the two is that the type of auto variables may be deduced from initializer lists, while the types of template parameters may … Read more
auto newvar1 = myvector; // vs: auto *newvar2 = myvector; Both of these are the same and will declare a pointer to std::vector<MyClass> (pointing to random location, since myvector is uninitialized in your example and likely contains garbage). So basically you can use any one of them. I would prefer auto var = getVector(), but … Read more
The const qualifier applies to the type to the immediate left unless there is nothing to the left then it applies to the type to the immediate right. So yup it’s the same.