Multiple templates singletons
Hi, I have a template class with 6 template arguments as : template <typename contractType, typename treeType, int n, enum1 rtype, enum2 qtype, enum3 vtype> class TreeImpl {}; I need to write partial specializations for the cases n=2, n=3, for 2 cases of rtype, 2 cases of qtype and 3 cases of vtype, therefore I will write 2*2*2*3 = 24 partial specializations. Any fully specialized template instance should be a singleton. I would like to find a way to store any instanciated full specialization in some common list, so that in other parts of the code, i can deal with the various singletons without having to write actual arguments n,rtype,qtype and vtype. I thought of having all these templates inherit from a template base class template <typename contractType, typename treeType> class TreeImplBase; Each specialization of these holds a static std::map< boost::tuple<int,enum1,enum2,enum3>, const TreeImplBase* >; which contains the list of the derived template classes. Any comments are appreciated, Perhaps this is a known design pattern, perhaps there is an easier way of doing this, perhaps there is a boost library which helps with this, regards,
Hello! I have a question to this construct: template <typename contractType, typename treeType>
class TreeImplBase;
Each specialization of these holds a static std::map< boost::tuple<int,enum1,enum2,enum3>, const TreeImplBase*
; which contains the list of the derived template classes.
How can you instantiate a pointer to the class temlate? Class template is an incomplete type. You will not be able to specify a pointer to it. I think you should use boost::fusion inplace. This lib, offers a compile time map (if you map the same time to an instance of it, use a fusion set), which can map a type to an instance. This is what you need. http://spirit.sourceforge.net/dl_more/fusion_v2/libs/fusion/doc/html/fusion/... http://spirit.sourceforge.net/dl_more/fusion_v2/libs/fusion/doc/html/fusion/...
Any comments are appreciated,
Perhaps this is a known design pattern, perhaps there is an easier way of doing this, perhaps there is a boost library which helps with this,
Good Luck, Ovanes
Ovanes Markarian wrote:
Hello!
I have a question to this construct:
template <typename contractType, typename treeType> class TreeImplBase;
Each specialization of these holds a static std::map< boost::tuple<int,enum1,enum2,enum3>, const TreeImplBase* >; which contains the list of the derived template classes.
How can you instantiate a pointer to the class temlate? Class template is an incomplete type. You will not be able to specify a pointer to it.
The wording is a bit ambiguous: A pointer to an /incomplete type/ is in fact OK (using standard terminology), but 'TreeImplBase' is a /template id/ which is not a type at all. As Ovanes pointed out that construct is illegal, however (except inside a definition of 'TreeImplBase' where it's the /injected class name/). /Specializing/ a template with template arguments yields a type. Using (whatever) member of this type's interface causes the template to be implicitly (possibly partially) /instantiated/. It's most important to realize that specializing a template does not cause the template to be instantiated automatically. Note that "template specialization" has a context-dependent meaning, as it can either refer to a type or of a class (template) definition of a variant implementation of the template: // /primary template/ template< typename T > struct A { ... }; // definition of the (full) specialization A<int> template< > struct A<int> { ... }; // definition of a partial specialization template< typename T > struct A< B<T> > { typedef A self; // /injected class name/ is a type }; // X and Y are specializations (not instantiations)! typedef A< B<int> > X; typedef A< long > Y; int main() { X x; // instantiation of the 'B<int>'-specialization of A // at this point // ... OK, that's about template terminology in five minutes :-). Regards, Tobias
Tobias, Thanks for your corrections. It is a bit difficult to speak by means of "C++-Standard Language" ;) With Kind Regards, Ovanes P.S. ---- OFFTOPIC Could you take a look at my previous posting regarding singleton destruction. May be you have overseen it. ---- END On Jan 24, 2008 3:26 PM, Tobias Schwinger <tschwinger@isonews2.com> wrote: [...]
The wording is a bit ambiguous: A pointer to an /incomplete type/ is in fact OK (using standard terminology), but 'TreeImplBase' is a /template id/ which is not a type at all.
As Ovanes pointed out that construct is illegal, however (except inside a definition of 'TreeImplBase' where it's the /injected class name/).
/Specializing/ a template with template arguments yields a type. Using (whatever) member of this type's interface causes the template to be implicitly (possibly partially) /instantiated/. It's most important to realize that specializing a template does not cause the template to be instantiated automatically.
Note that "template specialization" has a context-dependent meaning, as it can either refer to a type or of a class (template) definition of a variant implementation of the template:
// /primary template/ template< typename T > struct A { ... };
// definition of the (full) specialization A<int> template< > struct A<int> { ... };
// definition of a partial specialization template< typename T > struct A< B<T> > { typedef A self; // /injected class name/ is a type };
// X and Y are specializations (not instantiations)! typedef A< B<int> > X; typedef A< long > Y;
int main() { X x; // instantiation of the 'B<int>'-specialization of A // at this point
// ...
OK, that's about template terminology in five minutes :-).
Regards, Tobias
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Ovanes Markarian wrote:
Tobias,
Thanks for your corrections. It is a bit difficult to speak by means of "C++-Standard Language" ;)
Yes. Good practice nevertheless, because both error messages and formal texts (not at least the standard itself) use this terminology ;-). Regards, Tobias
I'm attempting to use Boost.Fusion under Boost.Spirit. I downloaded the library-only package as I already have boost 1.34.1 (which includes spirit but not fusion) However, under boost/spirit/fusion/, the structure of include dir is different from the includes in the http://spirit.sourceforge.net/dl_more/fusion_v2/libs/fusion/doc/html/fusion/ quick_start.html rds, From: boost-users-bounces@lists.boost.org [mailto:boost-users-bounces@lists.boost.org] On Behalf Of Ovanes Markarian Sent: 24 January 2008 15:52 To: boost-users@lists.boost.org Subject: Re: [Boost-users] Multiple templates singletons Tobias, Thanks for your corrections. It is a bit difficult to speak by means of "C++-Standard Language" ;) With Kind Regards, Ovanes P.S. ---- OFFTOPIC Could you take a look at my previous posting regarding singleton destruction. May be you have overseen it. ---- END On Jan 24, 2008 3:26 PM, Tobias Schwinger <tschwinger@isonews2.com> wrote: [...] The wording is a bit ambiguous: A pointer to an /incomplete type/ is in fact OK (using standard terminology), but 'TreeImplBase' is a /template id/ which is not a type at all. As Ovanes pointed out that construct is illegal, however (except inside a definition of 'TreeImplBase' where it's the /injected class name/). /Specializing/ a template with template arguments yields a type. Using (whatever) member of this type's interface causes the template to be implicitly (possibly partially) /instantiated/. It's most important to realize that specializing a template does not cause the template to be instantiated automatically. Note that "template specialization" has a context-dependent meaning, as it can either refer to a type or of a class (template) definition of a variant implementation of the template: // /primary template/ template< typename T > struct A { ... }; // definition of the (full) specialization A<int> template< > struct A<int> { ... }; // definition of a partial specialization template< typename T > struct A< B<T> > { typedef A self; // /injected class name/ is a type }; // X and Y are specializations (not instantiations)! typedef A< B<int> > X; typedef A< long > Y; int main() { X x; // instantiation of the 'B<int>'-specialization of A // at this point // ... OK, that's about template terminology in five minutes :-). Regards, Tobias _______________________________________________ Boost-users mailing list Boost-users@lists.boost.org http://lists.boost.org/mailman/listinfo.cgi/boost-users <http://lists.boost.org/mailman/listinfo.cgi/boost-users>
boost fusion has been separated from the spirit library. In Spirit you find the fusion 1.0. This is the link to the original review message, from there you can get separate fusion 2.0. I don't know if smth. changed in the lib, but getting the head revision of boost from subversion will provide you the latest sources of fusion: http://lists.boost.org/boost-announce/2006/05/0088.php Best Regards, Ovanes On Jan 25, 2008 6:47 PM, Hicham Mouline <hicham@mouline.org> wrote:
I'm attempting to use Boost.Fusion under Boost.Spirit.
I downloaded the library-only package as I already have boost 1.34.1(which includes spirit but not fusion)
However, under boost/spirit/fusion/, the structure of include dir is different from the includes in the
http://spirit.sourceforge.net/dl_more/fusion_v2/libs/fusion/doc/html/fusion/...
rds,
*From:* boost-users-bounces@lists.boost.org [mailto: boost-users-bounces@lists.boost.org] *On Behalf Of *Ovanes Markarian *Sent:* 24 January 2008 15:52 *To:* boost-users@lists.boost.org *Subject:* Re: [Boost-users] Multiple templates singletons
Tobias,
Thanks for your corrections. It is a bit difficult to speak by means of "C++-Standard Language" ;)
With Kind Regards, Ovanes
P.S. ---- OFFTOPIC Could you take a look at my previous posting regarding singleton destruction. May be you have overseen it. ---- END
On Jan 24, 2008 3:26 PM, Tobias Schwinger <tschwinger@isonews2.com> wrote: [...]
The wording is a bit ambiguous: A pointer to an /incomplete type/ is in fact OK (using standard terminology), but 'TreeImplBase' is a /template id/ which is not a type at all.
As Ovanes pointed out that construct is illegal, however (except inside a definition of 'TreeImplBase' where it's the /injected class name/).
/Specializing/ a template with template arguments yields a type. Using (whatever) member of this type's interface causes the template to be implicitly (possibly partially) /instantiated/. It's most important to realize that specializing a template does not cause the template to be instantiated automatically.
Note that "template specialization" has a context-dependent meaning, as it can either refer to a type or of a class (template) definition of a variant implementation of the template:
// /primary template/ template< typename T > struct A { ... };
// definition of the (full) specialization A<int> template< > struct A<int> { ... };
// definition of a partial specialization template< typename T > struct A< B<T> > { typedef A self; // /injected class name/ is a type };
// X and Y are specializations (not instantiations)! typedef A< B<int> > X; typedef A< long > Y;
int main() { X x; // instantiation of the 'B<int>'-specialization of A // at this point
// ...
OK, that's about template terminology in five minutes :-).
Regards, Tobias
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participants (3)
-
Hicham Mouline -
Ovanes Markarian -
Tobias Schwinger