Re: hash_map in STL.

From:

James Kanze <james.kanze@gmail.com>

Newsgroups:

comp.lang.c++

Date:

Thu, 20 Sep 2007 01:29:28 -0700

Message-ID:

<1190276968.808912.99610@57g2000hsv.googlegroups.com>

On Sep 19, 2:38 pm, Amit Bhatia <abha...@nospam.nospam.com> wrote:

I am trying to use hash maps from STL on gcc 3.3 as follows:

[Various attempts to create a member of Node which is a
hash_map of Nodes deleted...]

How can I fix this problem? If I want to use Node in hash_map, then I
can't use hash_map inside the class declaration.

Because hash_map, like the standard containers, requires a
complete type to be instantiated. And a class type is only
complete when the final } of the class definition has been seen.
The only solution is to introduce ponters or references
somewhere, e.g.:

    class Node
    {
    // ...
        hash_map< pair< int, int >, Node*, Node_Hasher >
                            parent ;
    } ;

or

    class Node
    {
    // ...
        hash_map< pair< int, int >, Node, Node_Hasher >*
                            parent ;
    } ;

(I suspect that the first is probably what you want anyway.)

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