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Andrew Maclean · Guest

OK I tried the microsoft.public.vc newsgroup and got no answer! So it looks
as if it is time to call in the experts! I really am stumped with this one
so any comments or help is appreciated.

In looking at the examplesat : http://www.josuttis.com/tmplbook/index.html
in particular, types/types/cpp and types/typet.hpp.
Has anyone been able to get it to compile for VC7.1?

The problem seems to lie in typet.hpp, namely the function:

template<typename T>
class IsFunctionT {
private:
typedef char One;
typedef struct { char a[2]; } Two;
template<typename U> static One test(...);
template<typename U> static Two test(U (*)[1]);
public:
enum { Yes = sizeof(IsFunctionT<T>::test<T>(0)) == 1 };
enum { No = !Yes };
};

The commpiler returns two errors:
c:BooksC++ Templatestypestypet.hpp(74): error C2783:
'IsFunctionT<T>::One IsFunctionT<T>::test(...)' : could not deduce template
argument for 'U'
with
[
T=int
]
and
c:BooksC++ Templatestypestypet.hpp(74): error C2784:
'IsFunctionT<T>::Two IsFunctionT<T>::test(U (*)[1])' : could not deduce
template argument for 'T1 (*)[1]' from 'int'
with
[
T=int
]

Note that to get this far you have to comment out the line contining the
macro:
MK_FUNDA_TYPE(wchar_t)
because wchar_t conflicts with unsigned short.

Interestingly the code built OK with GCC-3.1.0 however to build with
GCC-3.4.0 you have to change the line:
enum { Yes = sizeof(IsFunctionT<T>::test<T>(0)) == 1 };
to:
enum { Yes = sizeof(IsFunctionT<T>::template test<T>(0)) == 1 };
Which is fine.

So how do I help the compiler deduce the argument templates?

Please post any comments or help that you can give to the newsgroup.

Thanks
Andrew

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Sumit Rajan · Guest

"Andrew Maclean" <itsme (AT) gok (DOT) com> wrote

kostya · Guest

To compile with VC7.1 try that:
replace
template<typename T>
class IsFunctionT {
private:
typedef char One;
typedef struct { char a[2]; } Two;
template<typename U> static One test(...);
template<typename U> static Two test(U (*)[1]);
public:
enum { Yes = sizeof(IsFunctionT<T>::test<T>(0)) == 1 };
enum { No = !Yes };
};

with

typedef char One;
typedef struct { char a[2]; } Two;
template<typename U> One test(...);
template<typename U> Two test(U (*)[1]);

template<typename T>
class IsFunctionT {
public:
enum { Yes = sizeof(test<T>(0)) == 1 };
enum { No = !Yes };
};

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White Wolf · Guest

kostya wrote: