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c#c++varauto

Differences between C# "var" and C++ "auto"

I'm learning C++ now because I need to write some low level programs.

When I learned about auto keyword, it reminds me of the var keyword from C#.

So, what are the differences of C# var and C++ auto?

Solution

  • In C# var keyword works only locally inside function:

    var i = 10; // implicitly typed

    In C++ auto keyword can deduce type not only in variables, but also in functions and templates:

    auto i = 10;

auto foo() { //deduced to be int
    return 5;
}

template<typename T, typename U>
auto add(T t, U u) {
    return t + u;
}

    From performance point of view, auto keyword in C++ does not affect runtime performance. And var keyword does not affect runtime performance as well.

    Another difference can be in intellisense support in IDE. Var keyword in C# can be easily deduced and you will see the type with a mouse over. With auto keyword in C++ it might be more complicated, it depends on IDE and tooling.