janderson wrote:
> Hoenir wrote:
>> I still can't get the purpose of "auto".
>> I know it makes it possible to e.g. write "auto y = 4u;" but why not just "uint y = 4;"?
> 
> Its a generic/maintainable way of programming.  It means you can change the types your using without having to change ever reference to it.  It means you can copy paste or template a piece of code and have it work with little change.
> 
> It gets even more useful in larger programs when you start to layer this sort of general programming.
> 
> I hope that helps.

I should add, in the same vain (as others have mentioned in other ways), its useful for creating code that will work even when someone changes the interface.

-Joel

Bill Baxter wrote:
> Lacking any particular extenuating circumstances, I agree that that making types explicit is better than using auto.  But auto makes sense when
[list]

How about:
6) When the actual type may change later, and you want to make sure the variable is of the right type?

I've often found this to be very useful, especially since some implicit conversions can change the value (e.g. long -> int, signed/unsigned).

Bill Baxter escribió:
> Derek Parnell wrote:
>> On Wed, 20 Jun 2007 21:37:44 -0200, Ary Manzana wrote:
>>
>>> Derek Parnell escribió:
>>>> On Wed, 20 Jun 2007 14:20:43 +0200, Hoenir wrote:
>>>>
>>>>> I still can't get the purpose of "auto".
>>>>> I know it makes it possible to e.g. write "auto y = 4u;" but why not just "uint y = 4;"?
>>>>    auto y = someFunc();   // What type is it now?
>>>>
>>> // What can you do with y now, if you don't know the type?
>>
>> Pass it to a function that does know its type.
>>
> 
> I *think* the point was just that the code becomes less readable without any obvious indication of what type you've got.  Sure you can do all the same things you could do it the type were explicit, but someone else asked to fix this code is going to have to track down "someFunc()" to see what it returns.

Thanks for this! This is exacly my thought, although I couldn't have expressed myself that well.

I also agree with the situations you describe below, and also with number 6 of Frits. I'll not use it anywhere else, since having the type is more self documenting in a function.

> 
> Lacking any particular extenuating circumstances, I agree that that making types explicit is better than using auto.  But auto makes sense when
> 1) the actual type is a built-in (auto x = foo.length)
> 2) the actual type is obvious (auto x = new MyClass())
> 3) the actual type is huge/untypeable like
>    ( Node!(Node!(Node!(Expr!(Terminal!(1),Terminal!(2))))) x = expr!();
> 4) the actual type is unknowable (some template usages)
> 
> or
> 
> 5) when you're in a real hurry and don't have time to figure out what the actual type is.  :-)
> 
> --bb