c++ - Disallow function template instantiation with iterator parameter -

i have function template takes templated parameter:

template <class r> reft<r> make_ref(r& res) {     return reft<r>(&res); } 

i either want prevent r being kind of iterator, or, if easier, want have overload compiler prefer use iterators calls make_ref again iterator dereferenced.

best approach combining two, compiler prefers using iterator specific overload, , refuses use non-specific version.

i consumers of code able call make_ref(something) without having think whether something iterator or not - need different if is, , if that's not possible, give useful error message consumer.

first traits (you may have tweak requirements):

template <typename t> auto is_iterator_impl(t* it) -> decltype(**it, ++(*it), (*it) == (*it), std::true_type());  template <typename t> auto is_iterator_impl(...) -> std::false_type;  template <typename t> using is_an_iterator = decltype(is_iterator_impl<t>(0)); 

note: using std::iterator_traits<it> may alternative.

with sfinae, may do

template <class r> std::enable_if_t<!is_an_iterator<r>::value, reft<r>> make_ref(r& res) {     return reft<r>(&res); }  template <class r> std::enable_if_t<is_an_iterator<r>::value && !std::is_pointer<r>::value, reft<r>> // may want change return type make_ref(r& res) {     // implementation iterator }  template <class r> std::enable_if_t<std::is_pointer<r>::value, reft<r>> // may want change return type make_ref(r& res) {     // implementation iterator } 

note: want manage pointer differently, use std::is_pointer in addition custom is_an_iterator.

note: conditions should not have overlap, else have conflict.

live demo