Today, I noticed that lambda expressions accept arguments of type auto for example:
auto add = [](const auto& x, const auto& y)
{
return x + y;
}
So I tried with normal functions and it did not work:
auto add(const auto& x, const auto& y)
{
return x + y; //não compila
}
Can anyone explain why?
auto for lambda parameters exists to cover the fact that there is no way to specify generic types using template (the syntax would be strange). Well, that has changed in c ++ 20 , with the possibility of specifying them within lambda :
auto sum = []<typename T, typename U>(T a, U b) { return a + b; };
There is no auto for normal function parameters, because you can already specify generic types with template s:
template <typename T, typename U>
auto sum(T a, U b) -> decltype(a + b) { return a + b; }
It is a matter of lack of proposals to the committee itself. As far as I know, only an old TS of concepts proposed this use of auto , but it was removed.