How do I require const_iterator semantics in a template function signature?

Question

I am creating a constructor that will take a pair of input iterators. I want the method signature to have compile-time const semantics similar to:

DataObject::DataObject(const char *begin, const char *end)

However, I can't find any examples of this. For example, my STL implementation's range constructor for vector is defined as:

template<class InputIterator>
vector::vector(InputIterator first, InputIterator last)
{
    construct(first, last, iterator_category(first));
}

which has no compile-time const guarantees. iterator_category / iterator_traits<> contain nothing relating to const, either.

Is there any way to indicate to guarantee the caller that I can't modify the input data?

edit, 2010-02-03 16:35 UTC

As an example of how I would like to use the function, I would like to be able to pass a pair of char* pointers and know, based on the function signature, that the data they point at will not be modified.
I was hoping I could avoid creating a pair of const char* pointers to guarantee const_iterator semantics. I may be forced to pay the template tax in this case.

Answer 1

The caller can simply use the template with const iterators. If he does, and the compiler doesn't complain, it is guaranteed that the function doesn't modify the data. If it would modify the data, instantiating the template with a const iterator would lead to errors.

You don't really have to force the caller to use const iterators just because you don't modify anything.

Answer 2

You could simply create a dummy function which calls your template with char * const pointers. If your template attempts to modify their targets, then your dummy function will not compile. You can then put said dummy inside #ifndef NDEBUG guards to exclude it from release builds.