Thread: Automatic variable

Hello everyone,


I have searched and found the term automatic variable means function local variable, compared with static and global variable. Is that correct?


thanks in advance,
George

It means a variable that will be destroyed as soon as it goes out of scope (i.e. not a pointer, since you manually have to free() them)

I think I've also seen an auto keyword, although I don't see why you would ever need to use it since it's auto by default?

Originally Posted by cpjust

It means a variable that will be destroyed as soon as it goes out of scope (i.e. not a pointer, since you manually have to free() them)

I think I've also seen an auto keyword, although I don't see why you would ever need to use it since it's auto by default?

I, for one, am glad for the presence of the auto keyword. There are rumblings afoot that this keyword will be co-opted to a new use in the new C++ standard. It will mean "whatever type makes this declaration valid." Should prove extremely useful for metaprogramming.

Example

Code:

auto x = boost::some_crazy_object();

Where the type of boost::some_crazy_object() might be some enormous 5000-character long template typename, which you neither care to infer nor could even if you wanted to. "auto" in this case means "that type," so you can easily declare x without having to figure out what exact type is being used.

Also, I hope they allow it for return types from template functions (allowing it for normal functions would be unreasonable and probably impossible to implement):

Code:

template <typename T>
auto my_func(T blah)
{
    return some_crazy_thing(blah);
}

Where the return type is whatever type some_crazy_thing(blah) is.

Can't wait!

Originally Posted by brewbuck

I, for one, am glad for the presence of the auto keyword. There are rumblings afoot that this keyword will be co-opted to a new use in the new C++ standard. It will mean "whatever type makes this declaration valid." Should prove extremely useful for metaprogramming.

Example

Code:

auto x = boost::some_crazy_object();

Where the type of boost::some_crazy_object() might be some enormous 5000-character long template typename, which you neither care to infer nor could even if you wanted to. "auto" in this case means "that type," so you can easily declare x without having to figure out what exact type is being used.

Also, I hope they allow it for return types from template functions (allowing it for normal functions would be unreasonable and probably impossible to implement):

Code:

template <typename T>
auto my_func(T blah)
{
    return some_crazy_thing(blah);
}

Where the return type is whatever type some_crazy_thing(blah) is.

Can't wait!

I highly doubt they would change the meaning of auto since it would completely break backwards compatibility with C & current C++.

Originally Posted by cpjust

I highly doubt they would change the meaning of auto since it would completely break backwards compatibility with C & current C++.

It's being seriously discussed. Might not happen but I don't "highly doubt" it.