A problem about explicit instantiation of class template

[yuanhp_china]

I define a class in A.h:

template <class Tclass A{

public:
void get_elem( const T&) ;
};

Then I give the implementation in A.cpp (and do an explicit
instantiation ):

template<class Tvoid A::get_elem( const T&)
{...}

template class A<int>; //explicit instantiation


I have another two files: main.cpp and B.cpp. I would like to reuse
the explicit instantiation of A<intof A.cpp in the two files. Do I
need to declare class A<intin the two files? I am not sure how to do
it?

Any help are appreciated.
Hua

[Barry]

yu**********@ho tmail.com wrote:

I define a class in A.h:

template <class Tclass A{

public:
void get_elem( const T&) ;
};

Then I give the implementation in A.cpp (and do an explicit
instantiation ):

Separating a template class into hxx file and cxx file should be done
with keyword 'export' support, which is rarely supported by compilers
(IIRC, Comeau supports it).

So when you define a template class, just put all the implementation in
hxx files.

>
template<class Tvoid A::get_elem( const T&)
{...}

template class A<int>; //explicit instantiation


I have another two files: main.cpp and B.cpp. I would like to reuse
the explicit instantiation of A<intof A.cpp in the two files. Do I
need to declare class A<intin the two files? I am not sure how to do
it?

Don't worry about the duplicated instantiation, the compiler is smart
enough to know which she's already instantiated.

Any help are appreciated.

I think you should find a textbook to start with template programming first.

[Salt_Peter]

On Jan 1, 1:35 am, yuanhp_ch...@ho tmail.com wrote:

I define a class in A.h:

template <class Tclass A{

public:
void get_elem( const T&) ;

};

Then I give the implementation in A.cpp (and do an explicit
instantiation ):

template<class Tvoid A::get_elem( const T&)
{...}

template class A<int>; //explicit instantiation

I have another two files: main.cpp and B.cpp. I would like to reuse
the explicit instantiation of A<intof A.cpp in the two files. Do I
need to declare class A<intin the two files? I am not sure how to do
it?

Any help are appreciated.

Hua

Have you consulted the FAQ?
[35.15] How can I avoid linker errors with my template classes?
http://www.parashift.com/c++-faq-lit...html#faq-35.15

[qqq]

On Jan 1, 3:24*am, Barry <dhb2...@gmail. comwrote:

yuanhp_ch...@ho tmail.com wrote:

I define aclassin A.h:

template<classT >classA{

public:
* * void get_elem( const T&) ;
};

Then I give the implementation in A.cpp (and do anexplicit
instantiation):

Separating atemplateclassi nto hxx file and cxx file should be done
with keyword 'export' support, which is rarely supported by compilers
(IIRC, Comeau supports it).

So when you define atemplateclass, just put all the implementation in
hxx files.

template<classT void A::get_elem( const T&)
*{...}

templateclassA< int>; //explicitinstant iation

I have another two files: main.cpp and B.cpp. I would like to reuse
theexplicitinst antiationof A<intof A.cpp in the two files. Do I
need to declareclassA<i ntin the two files? I am not sure how to do
it?

Don't worry about the duplicatedinsta ntiation, the compiler is smart
enough to know which she's already instantiated.

Any help are appreciated.

I think you should find a textbook to start withtemplatepro gramming first.

Thanks for your reply. I have read many c++ books, but no one talk
the explicit instantiation very well.

I prefer to the explicit instantiation instead of inline. But when I
do an explicit instantiation in one .cpp file, I got some link error
when more than one files are needing to use the explicit instantiation
(if just one file, it can work.).

[Barry]

qqq wrote:

On Jan 1, 3:24 am, Barry <dhb2...@gmail. comwrote:

>yuanhp_ch...@h otmail.com wrote:

>>I define aclassin A.h:
template<clas sT>classA{
public:
void get_elem( const T&) ;
};
Then I give the implementation in A.cpp (and do anexplicit
instantiation ):

Separating atemplateclassi nto hxx file and cxx file should be done
with keyword 'export' support, which is rarely supported by compilers
(IIRC, Comeau supports it).

So when you define atemplateclass, just put all the implementation in
hxx files.

>>template<clas sTvoid A::get_elem( const T&)
{...}
templateclass A<int>; //explicitinstant iation
I have another two files: main.cpp and B.cpp. I would like to reuse
theexplicitin stantiationof A<intof A.cpp in the two files. Do I
need to declareclassA<i ntin the two files? I am not sure how to do
it?

Don't worry about the duplicatedinsta ntiation, the compiler is smart
enough to know which she's already instantiated.

>>Any help are appreciated.

I think you should find a textbook to start withtemplatepro gramming first.

Thanks for your reply. I have read many c++ books, but no one talk
the explicit instantiation very well.

I prefer to the explicit instantiation instead of inline. But when I
do an explicit instantiation in one .cpp file, I got some link error
when more than one files are needing to use the explicit instantiation
(if just one file, it can work.).

I didn't mean reading a textbook about "template explicit
instantiation", which is quite a rarely(at least for me) used language
feature.

http://www.codeproject.com/KB/cpp/te...sourceorg.aspx