Re: [boost] auto (was Most needed/desired features in C++)

From: Howard Hinnant (hinnant_at_[hidden])
Date: 2002-02-19 14:39:20

On Tuesday, February 19, 2002, at 02:13  PM, Gary Powell wrote:

>>> ---------------------------------
> If the return expression includes anything else, including more than one
> auto variables, it could involve an implicit conversion.
>
> template<typename A, typename B>
> auto operator+(A a, B b)
> {
>   return a + b;  // posible implicit conversion here.
> }
> <<--------------------------------------------------
> Yes!
> And we don't know what that conversion is! And we can't ask the
> compiler to tell us. Instead in LL, we had to do pages of
> type deduction code that "knows" what the conversions are. And
> if you are using a user defined class that has overloaded
> operator +() you have to tell us what the return type is. Its
> arcane, and the compiler does know it. But we can't find out.
> And we don't really care what it is, other than to pass it
> along to the calling function.
>
> You wouldn't believe what a killer issue this is until you
> try it. (Jeremy S. knows that's for sure, as does Peter D.)

You could find out with typeof(a+b).

That's not a plug for auto or typeof.  I was just too amused to be 
quiet. :-)

-Howard