Re: Isn't 'std:.string::npos' an integral constant?

From:
James Kanze <james.kanze@gmail.com>
Newsgroups:
comp.lang.c++
Date:
Tue, 23 Sep 2008 00:51:39 -0700 (PDT)
Message-ID:
<477131d3-4c53-4c8d-b400-e260b78d8e87@w7g2000hsa.googlegroups.com>
On Sep 22, 11:50 pm, Paavo Helde <nob...@ebi.ee> wrote:

Hendrik Schober <spamt...@gmx.de> kirjutas:

  Interestingly, Comeau compile this
     struct test1 {
       static const int x = -1;
     };

     struct test2 {
       static const int x = test1::x;
     };
   without any complaints. However, it compiles this
     struct test1 {
       static const int x;
     };
     const int test1::x = 1;

     struct test2 {
       static const int x = test1::x;
     };
   just as well.


Indeed. However, if test1 is a template, it fails. Seems a bit
inconsistent.


Not really. A template definition is not a variable definition;
only the instantiation of a template definition is a variable
definition. And the "point of instantiation" of a member
function or member static variable is immediately following the
namespace scope declaration which triggers the instantiation.
So if you write:

    template< typename T >
    struct test1
    {
        static int const x ;
    } ;

    template< typename T >
    int const test1::x = 1 ;

    struct test2
    {
        static int const x = test1< int >::x ;
    } ;

, the compiler inserts the instantiation of the class test1<int>
immediately before the definition of test2, and the
instantiation of the static data member immediately after, i.e.:

    struct test1< int >
    {
        static int const x ;
    } ;

    struct test2
    {
        static int const x = test1< int >::x ;
    } ;
    int const test1< int >::x = 1 ;

And the value of test1< int >::x isn't visible when test2::x is
declared.

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