Ambiguous template class constructor

Question

I'm implementing a N-dimensional array library. Consider this code:

template<int Rank, class Type>
class Array {
{
public:
    // constructor for vectors, valid when Rank==1
    Array(int dim0, Type val = Type());

    // constructor for matrices, valid when Rank==2
    Array(int dim0, int dim1, Type val = Type());
    ...
}

The problem is that if Type == int, the compiler will complain about ambiguous constructor call (for example, Array<1,int>(1,1)). Is there a trick like enable_if that makes the compiler ignore constructors that don't match Rank? (without C++11 please)

Thank you

@Daniel Ops, it should be `int Rank`, sorry. – montefuscolo Sep 10 '13 at 18:46 — montefuscolo, Sep 10 '13 at 18:46

score 1 · Accepted Answer · answered Sep 10 '13 at 18:51

You could use template specialization for this:

template<int size, class Type>
class Array {
// General stuff for size > 2, if you have any
};


template <class Type>
class Array<1, Type>
{
// Code for one-dimensional array
};


template <class Type>
class Array<2, Type>
{
// Code for two-dimensional array
};

or even specify it for int exactly:

template <>
class Array<2, int>
{
// Code for two-dimensional integer array
};

It is also perfectly valid for them to have totally different set of public interfaces.

But I would probably pass an array or std::vector of given size for dimensions or remove the third argument, just add a method, say, populate(Type t) to do the trick (and it may be also useful not only for constructing).

Ambiguous template class constructor

1 Answers1