Hi,
I have a problem, that boils down to the following code:
#include <iostream>
#include <typeinfo>
class Test1 {};
class Test2 {};
class Test3 {};
template< typename T >
struct Cont { T t; };
template< typename T >
class TT { public: TT(T) {} };
struct X {
template< template<typename> class TT, typename T >
static void f(const T& t)
{
std::cout << '\t' << typeid(t).name() << std::endl;
}
template< template<typename> class TT >
static void f(const Test3& t)
{
std::cout << '\t' << typeid(t).name() << std::endl;
}
template< template<typename> class TT, typename T >
static void f(const Cont<T>& c)
{
f<TT>( c.t ); // <== error here
}
};
int main()
{
Cont<Test1> c1;
Cont<Test2> c2;
Cont<Test3> c3;
X::f< TT, Test1 >(c1);
X::f< TT, Test2 >(c2);
X::f< TT, Test3 >(c3);
return 0;
}
For this Comeau and CW9 report (in the line marked
"error here") that the call is ambigous. (VC7.1
accepts the code, BTW.)
First, I don't see what's wrong, but overloading
rules, especially in conjunctions with templates,
are too complicated for me to remember them anyway.
Second, I need a solution. I'm sure I would get it
to work if I would use a class template and partial
specialize it. However, the original code is long
and complex enough without yet another helper class
template...
I would hope that, once the problem is known, a
simpler way could be found. AFAIK, function template
overloading _is_ possible, after all.
TIA,
Schobi
-- Sp******@gmx.de is never read
I'm Schobi at suespammers dot org
"Sometimes compilers are so much more reasonable than people."
Scott Meyers 7 1976
On Fri, 30 Apr 2004 16:28:28 +0200, "Hendrik Schober" <Sp******@gmx.de>
wrote: Hi,
I have a problem, that boils down to the following code:
#include <iostream> #include <typeinfo>
class Test1 {}; class Test2 {}; class Test3 {};
template< typename T > struct Cont { T t; };
template< typename T > class TT { public: TT(T) {} };
struct X {
template< template<typename> class TT, typename T > static void f(const T& t) { std::cout << '\t' << typeid(t).name() << std::endl; }
template< template<typename> class TT > static void f(const Test3& t) { std::cout << '\t' << typeid(t).name() << std::endl; }
template< template<typename> class TT, typename T > static void f(const Cont<T>& c) { f<TT>( c.t ); // <== error here }
};
int main() { Cont<Test1> c1; Cont<Test2> c2; Cont<Test3> c3;
X::f< TT, Test1 >(c1); X::f< TT, Test2 >(c2); X::f< TT, Test3 >(c3);
return 0; }
For this Comeau and CW9 report (in the line marked "error here") that the call is ambigous. (VC7.1 accepts the code, BTW.) First, I don't see what's wrong, but overloading rules, especially in conjunctions with templates, are too complicated for me to remember them anyway. Second, I need a solution. I'm sure I would get it to work if I would use a class template and partial specialize it. However, the original code is long and complex enough without yet another helper class template... I would hope that, once the problem is known, a simpler way could be found. AFAIK, function template overloading _is_ possible, after all.
Perhaps you've OVER-simplified, because it is not clear to my why you have
the template-template parameter there in your templates. I'm not sure, but
if it were used perhaps there might be more of a handle to be had on how to
disambiguate your calls. If you don't really need that
template-template-parameter, then your class can just be this:
struct X {
// template< template<typename> class TT, typename T >
template<typename T >
static void f(const T& t)
{
std::cout << '\t' << typeid(t).name() << std::endl;
}
// template< template<typename> class TT >
static void f(const Test3& t)
{
std::cout << '\t' << typeid(t).name() << std::endl;
}
template< template<typename> class TT, typename T >
static void f(const Cont<T>& c)
{
f( c.t ); // <== error here
}
};
-leor TIA,
Schobi
--
Leor Zolman --- BD Software --- www.bdsoft.com
On-Site Training in C/C++, Java, Perl and Unix
C++ users: download BD Software's free STL Error Message Decryptor at: www.bdsoft.com/tools/stlfilt.html
Leor Zolman <le**@bdsoft.com> wrote: [...] Perhaps you've OVER-simplified, because it is not clear to my why you have the template-template parameter there in your templates.
Yes, that's due to the simplification.
In the real code, the template template
arg is used to pick some algorithms that
are to be applied. They are vital to
these functions. :(
I'm not sure, but if it were used perhaps there might be more of a handle to be had on how to disambiguate your calls. If you don't really need that template-template-parameter, then your class can just be this:
struct X {
// template< template<typename> class TT, typename T > template<typename T > static void f(const T& t) { std::cout << '\t' << typeid(t).name() << std::endl; }
// template< template<typename> class TT > static void f(const Test3& t) { std::cout << '\t' << typeid(t).name() << std::endl; }
template< template<typename> class TT, typename T > static void f(const Cont<T>& c) { f( c.t ); // <== error here }
};
I am surprised. Why would the other template arg
cause the call to be ambiguos?
-leor
Schobi
-- Sp******@gmx.de is never read
I'm Schobi at suespammers dot org
"Sometimes compilers are so much more reasonable than people."
Scott Meyers
On Fri, 30 Apr 2004 16:53:59 +0200, "Hendrik Schober" <Sp******@gmx.de>
wrote: I'm not sure, but if it were used perhaps there might be more of a handle to be had on how to disambiguate your calls. If you don't really need that template-template-parameter, then your class can just be this:
struct X {
// template< template<typename> class TT, typename T > template<typename T > static void f(const T& t) { std::cout << '\t' << typeid(t).name() << std::endl; }
// template< template<typename> class TT > static void f(const Test3& t) { std::cout << '\t' << typeid(t).name() << std::endl; }
template< template<typename> class TT, typename T > static void f(const Cont<T>& c) { f( c.t ); // <== error here }
}; I am surprised. Why would the other template arg cause the call to be ambiguos?
Because in my simplified version, that second version of f is not a
template.
-leor -leor
Schobi
--
Leor Zolman --- BD Software --- www.bdsoft.com
On-Site Training in C/C++, Java, Perl and Unix
C++ users: download BD Software's free STL Error Message Decryptor at: www.bdsoft.com/tools/stlfilt.html
Leor Zolman <le**@bdsoft.com> wrote: [...] Because in my simplified version, that second version of f is not a template.
<ahem>
Right. Sorry for that stupid question.
-leor
Schobi
-- Sp******@gmx.de is never read
I'm Schobi at suespammers dot org
"Sometimes compilers are so much more reasonable than people."
Scott Meyers
Hendrik Schober wrote in news:c6**********@news1.transmedia.de in
comp.lang.c++: Hi,
I have a problem, that boils down to the following code:
#include <iostream> #include <typeinfo>
class Test1 {}; class Test2 {}; class Test3 {};
template< typename T > struct Cont { T t; };
template< typename T > class TT { public: TT(T) {} };
struct X {
template< template<typename> class TT, typename T > static void f(const T& t) { std::cout << '\t' << typeid(t).name() << std::endl; }
Here's a Hack-around:
template< template<typename> class TT, typename T >
static void f(const volatile T& tv)
{
T const &t = const_cast< T const & >( tv );
std::cout << '\t' << typeid(t).name() << std::endl;
}
template< template<typename> class TT > static void f(const Test3& t) { std::cout << '\t' << typeid(t).name() << std::endl; }
template< template<typename> class TT, typename T > static void f(const Cont<T>& c) { f<TT>( c.t ); // <== error here }
};
int main() { Cont<Test1> c1; Cont<Test2> c2; Cont<Test3> c3;
X::f< TT, Test1 >(c1); X::f< TT, Test2 >(c2); X::f< TT, Test3 >(c3);
return 0; }
For this Comeau and CW9 report (in the line marked "error here") that the call is ambigous. (VC7.1 accepts the code, BTW.)
Neither is a better match (they're both exact) and neither is more
specialized, and since there is no such thing as a function partial
specailization, we can't make it so.
First, I don't see what's wrong, but overloading rules, especially in conjunctions with templates, are too complicated for me to remember them anyway. Second, I need a solution. I'm sure I would get it to work if I would use a class template and partial specialize it. However, the original code is long and complex enough without yet another helper class template... I would hope that, once the problem is known, a simpler way could be found. AFAIK, function template overloading _is_ possible, after all.
I Think Comeau/CW (also g++ 3.2 & 3.4 pre-release) is correct here.
Though I wouldn't bet my shirt on it.
Rob.
-- http://www.victim-prime.dsl.pipex.com/
Rob Williscroft <rt*@freenet.co.uk> wrote: [...] Here's a Hack-around:
template< template<typename> class TT, typename T > static void f(const volatile T& tv) { T const &t = const_cast< T const & >( tv ); std::cout << '\t' << typeid(t).name() << std::endl; }
Ugh.
[...]
Neither is a better match (they're both exact) and neither is more specialized,
I always thought a types always is a
better match than a template arg?
Well, I guess I'm wrong...
and since there is no such thing as a function partial specailization, we can't make it so.
I was afraid I'd have to create a helper
class template.
[...] Rob.
Thanks,
Schobi
-- Sp******@gmx.de is never read
I'm Schobi at suespammers dot org
"Sometimes compilers are so much more reasonable than people."
Scott Meyers
Hendrik Schober <Sp******@gmx.de> wrote: [...]
Thanks to everybody who cared. I found this:
template< template<typename> class TT, typename T >
static void f(const T& t, CBool<false> /*isTest3*/)
{
std::cout << '\t' << typeid(t).name() << std::endl;
}
template< template<typename> class TT, typename T >
static void f(const T& t, CBool<true> /*isTest3*/)
{
std::cout << '\t' << typeid(t).name() << std::endl;
}
template< template<typename> class TT, typename T >
static void f(const Cont<T>& c)
{
f<TT>( c.t, CBool<CIsSameType<T,Test3>::result>() );
}
Comeau accepts it, so I assume it's OK...
Schobi
-- Sp******@gmx.de is never read
I'm Schobi at suespammers dot org
"Sometimes compilers are so much more reasonable than people."
Scott Meyers This thread has been closed and replies have been disabled. Please start a new discussion. Similar topics
by: Terje Slettebø |
last post by:
To round off my trilogy of "why"'s about PHP... :) If this subject have been
discussed before, I'd appreciate a pointer to it. I again haven't found it
in a search of the PHP groups.
The PHP...
|
by: Dave Theese |
last post by:
Hello all,
I'm trying to get a grasp of the difference between specializing a function
template and overloading it. The example below has a primary template, a
specialization and an overload. ...
|
by: Leslaw Bieniasz |
last post by:
Cracow, 20.09.2004
Hello,
I need to implement a library containing a hierarchy of classes
together with some binary operations on objects. To fix attention,
let me assume that it is a...
|
by: franklini |
last post by:
hello people i. can anybody help me, i dont know what is wrong with
this class. it has something to do with the me trying to override the
input output stream. if i dont override it, it works fine....
|
by: WittyGuy |
last post by:
Hi,
What is the major difference between function overloading and function
templates?
Thanks!
http://www.gotw.ca/resources/clcm.htm for info about ]
|
by: zeus |
last post by:
I know function overloading is not supported in C.
I have a few questions about this:
1. Why? is it from technical reasons? if so, which?
2. why wasn't it introduced to the ANSI?
3. Is there any...
|
by: recover |
last post by:
#include <stdio.h>
template<class T>
class TpHello
{
public:
int GetHash(){return 0;}
protected:
private:
T a;
|
by: nyl2002 |
last post by:
I have written the following very short template class in testclass.h:
template<typename C,typename T>
class TestClass {
public:
TestClass() {};
~TestClass();
private:
T testFunction(T...
|
by: iu2 |
last post by:
Hi all, can someone help me with this?
I'm trying to shorthen some logging function in our project, i.e.,
instead of
LogString("...);
use a more convenient
log() << "String here " <<...
|
by: emmanuelkatto |
last post by:
Hi All, I am Emmanuel katto from Uganda. I want to ask what challenges you've faced while migrating a website to cloud.
Please let me know.
Thanks!
Emmanuel
|
by: BarryA |
last post by:
What are the essential steps and strategies outlined in the Data Structures and Algorithms (DSA) roadmap for aspiring data scientists? How can individuals effectively utilize this roadmap to progress...
|
by: nemocccc |
last post by:
hello, everyone, I want to develop a software for my android phone for daily needs, any suggestions?
|
by: Sonnysonu |
last post by:
This is the data of csv file
1 2 3
1 2 3
1 2 3
1 2 3
2 3
2 3
3
the lengths should be different i have to store the data by column-wise with in the specific length.
suppose the i have to...
|
by: Hystou |
last post by:
There are some requirements for setting up RAID:
1. The motherboard and BIOS support RAID configuration.
2. The motherboard has 2 or more available SATA protocol SSD/HDD slots (including MSATA, M.2...
|
by: Hystou |
last post by:
Most computers default to English, but sometimes we require a different language, especially when relocating. Forgot to request a specific language before your computer shipped? No problem! You can...
|
by: jinu1996 |
last post by:
In today's digital age, having a compelling online presence is paramount for businesses aiming to thrive in a competitive landscape. At the heart of this digital strategy lies an intricately woven...
|
by: isladogs |
last post by:
The next Access Europe User Group meeting will be on Wednesday 1 May 2024 starting at 18:00 UK time (6PM UTC+1) and finishing by 19:30 (7.30PM).
In this session, we are pleased to welcome a new...
|
by: conductexam |
last post by:
I have .net C# application in which I am extracting data from word file and save it in database particularly. To store word all data as it is I am converting the whole word file firstly in HTML and...
| |