Re: Template question...
Andy wrote:
A template questions I'm hoping someone might be able to help me with.
First off, I have a template defined something like,
template <int Count>struct ACollectionOfThings
{
// Definition of a collection that contains exactly Count things.
};
I would like to be able to stop people using this class with certain
values of Count, as an example I also have a template,
template <int Count>struct ASmallCollectionOfThings
{
// Definition of a collection that contains exactly Count things.
};
And I would like people to use the Small collection for values of
Count less than some number, so I would like a compile time error to
be issued when someone did,
CollectionOfThings<ASmallNumber> ACollection;
How would I go about making this happen?
template<int Count> struct ACollectionOfThings {
typedef char not_allowed[Count > 16];
not_allowed& foo(); // dummy member
};
template<int Count> struct ASmallCollectionOfThings {
typedef char not_allowed[Count <= 16];
not_allowed& foo(); // dummy member
};
int main()
{
ACollectionOfThings<123> c123; // OK
ACollectionOfThings<10> c10; // causes an error
ASmallCollectionOfThings<10> sc10; // OK
ASmallCollectionOfThings<123> sc123; // causes an error
return 0;
}
V
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