Question

I need to develop an algorithm for a library that receives a “list of strings”.

Of course I want to pass an “abstract” iterator to decouple the internal representation of that list (a vector, a linked list, a map…) to the access to it from my function.

This is my approach:

template <typename ForwardIterator>
void myAlgorithm(ForwardIterator itBegin, ForwardIterator itEnd) {
   for(; itBegin != itEnd ; ++itBegin) {
       // Do something with *itBegin
   }
}

My question is, how can I restrict the type of the container to be string? Or even more, is there some way of accepting both std::strings and char* as elements?

Thanks a lot.

Answer 1

Use a static assertion along with std::iterator_traits<>:

template<typename ForwardIterator>
void myAlgorithm(ForwardIterator itBegin, ForwardIterator itEnd) {
    typedef typename std::iterator_traits<ForwardIterator>::value_type value_t;
    BOOST_STATIC_ASSERT((
        boost::is_same<value_t, std::string>::value ||
        boost::is_same<value_t, char const*>::value
    ));

    for(; itBegin != itEnd ; ++itBegin) {
        // Do something with *itBegin
    }
}

If you’re using a C++0x compiler, you can use static_assert instead of BOOST_STATIC_ASSERT and std::is_same instead of boost::is_same.