Re: [eigen] Can we prevent that this compiles?

[Markus Moll <markus.moll@xxxxxxxxxxxxxxxx>]

Hi

Another alternative is having a templated constructor which is a better match 
for types other than T:

template<typename T, [...]>
class Replicate
{
	[...]

	template<typename U> struct dummy;

	Replicate(const T& t);
	template<typename U> Replicate(const U& u) { dummy<U>::template 
ConstructionOnlyPossibleFromType<T>; }

	[...]
};

int main()
{
	SomeClass obj;
	Replicate<SomeOtherClass> r( obj );	
}

Here, gcc emits an error like:
: In constructor ‘X<T>::X(const U&) [with U = SomeClass, T = SomeOtherClass]’:
:  instantiated from here
: error: ‘ConstructionOnlyPossibleFrom<T>’ is not a member of 
		‘X<SomeOtherClass>::dummy<SomeClass>’

Does anyone see any problem with either of these approaches?
If not, I guess it's a matter of taste.
Personally, I think the solution posted earlier is cleaner.

Markus

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