Possible to partially typedef templates?

[esuvs81@googlemail.com]

Hi all, i have a Vector class (as in mathematical vectors) which is
templatised on two parameters, the length of the vector and it's type
(int,double,etc ). I am able to use a typedef like the folowing:

typedef Vector<3,floatV ector3DFloat;
Vector3DFloat myVector;

so that users can now use Vector3DFloat as a type in thier code.
However, i would like to just typedef away *one* of the parameters
which i would expect to look something like the following:

typedef Vector<3,TypeVe ctor3D<Type>;
Vector3D<floatm yVector;

The above doesn'tcompile but hopefully illustrates what I am trying to
do. Is there a way to make this work?

Thanks,

David

[jpalecek@web.de]

Re: Possible to partially typedef templates?


esuvs81@googlem ail.com napsal:

Hi all, i have a Vector class (as in mathematical vectors) which is
templatised on two parameters, the length of the vector and it's type
(int,double,etc ). I am able to use a typedef like the folowing:
>
typedef Vector<3,floatV ector3DFloat;
Vector3DFloat myVector;
>
so that users can now use Vector3DFloat as a type in thier code.
However, i would like to just typedef away *one* of the parameters
which i would expect to look something like the following:
>
typedef Vector<3,TypeVe ctor3D<Type>;
Vector3D<floatm yVector;
>
The above doesn'tcompile but hopefully illustrates what I am trying to
do. Is there a way to make this work?

No, there's no elegant solution to this. C++0x will (hopefully) have
"template
typedefs", which is just what you want. If you want further details
including possible workarounds, see

http://www.ddj.com/dept/cpp/184403850

Regards
Jiri Palecek

[amparikh@gmail.com]

Re: Possible to partially typedef templates?


esuvs81@googlem ail.com wrote:

Hi all, i have a Vector class (as in mathematical vectors) which is
templatised on two parameters, the length of the vector and it's type
(int,double,etc ). I am able to use a typedef like the folowing:
>
typedef Vector<3,floatV ector3DFloat;
Vector3DFloat myVector;
>
so that users can now use Vector3DFloat as a type in thier code.
However, i would like to just typedef away *one* of the parameters
which i would expect to look something like the following:
>
typedef Vector<3,TypeVe ctor3D<Type>;
Vector3D<floatm yVector;
>
The above doesn'tcompile but hopefully illustrates what I am trying to
do. Is there a way to make this work?
>
Thanks,
>
David

You cannot typedef templates with the template parameters. However you
can simulate the effect by introducing an intermediate type.
You can refer to Herb Sutter's GOTW here..

http://www.gotw.ca/gotw/079.htm

[esuvs81@googlemail.com]

Re: Possible to partially typedef templates?

Ok, thanks to both of you. It looks like i can get around the problem
with Herb Sutters solution until C++0x arrives...

Thanks again,

David