TITLE: initialising STL containers

(Newsgroups: comp.lang.c++.moderated, 5 May 2000)

MERRICK: "Steve Merrick" <Steve.Merrick@marconicomms.com>

> If I have an array full of fixed data, I used
> to type:
>
> int array[] = {1, 2, 3, 4};
>
> and that was that. There doesn't seem to be an equivalent syntax for
> vectors:
>
> vector<int> array = {1, 2, 3, 4};  // Illegal!
> vector<int> array(1, 2, 3, 4);     // Illegal!
> // and so on...
>
> Instead, I have to initialise a C-style array, and manually move its
> contents into a vector. Is there a means of initialising a vector in this
> way, or must I stick with C-style arrays for this purpose?

AUSTERN: Matt Austern <austern@sgi.com>

No, and no.

You can't use a vector, because this initialization syntax only works
for aggregates.  (See section 8.5.1 of the C++ standard.)  The class
std::vector isn't an aggregate because it has user-defined
constructors, it has private or protected data, and it might have base
classes.

However, you don't have to stick with C-style arrays.  You can use an
STL container class, it just can't be any of the STL container classes
in the C++ standard.  You can use a simple fixed-size container;
Bjarne Stroustrup writes about a container called 'c_array' in the
latest edition of _The C++ Programming Language_, and I write about a
container called 'block' in my book.  So, for example, you can write:

    block<int, 4> array = {1, 2, 3, 4};



_______________________________________________
cpptips mailing list
http://cpptips.hyperformix.com