std::transform(std::begin(a), std::end(a), std::begin(b), [](int a){return a + 50;});

std::transform(std::begin(a), std::end(a), std::begin(b), [](auto a){return a + 50;});

auto DeduceReturnType(); // Return type to be determined.
If multiple return expressions are used in the function's implementation, then they must all deduce the same type.[7]
Functions that deduce their return types can be forward declared, but they cannot be used until they have been defined. Their definitions must be available to the translation unit that uses them.
Recursion can be used with a function of this type, but the recursive call must happen after at least one return statement in the definition of the function:[7]
auto Correct(int i) {
if (i == 1)
return i; // return type deduced as int
else
return Correct(i-1)+i; // ok to call it now
}

auto Wrong(int i)
{
if(i != 1)
return Wrong(i-1)+i; // Too soon to call this. No prior return statement.
else
return i; // return type deduced as int
}