fork download

copy

    #include <type_traits>
    #include <iterator>
    #include <vector>
 
    template<typename T, typename = void>
    struct is_const_iterator : std::false_type { };
 
    template<typename T>
    struct is_const_iterator<T,
        typename std::enable_if<
            std::is_const<
                typename std::remove_pointer<
                    typename std::iterator_traits<T>::pointer
                    >::type
                >::value
            >::type> : std::true_type { };
 
    template<typename It,
        typename std::enable_if<!is_const_iterator<It>::value>::type* = nullptr>
    void foo(It i)
    {
        // Does something with i...
    }
 
    int main()
    {
        std::vector<int> v;
        foo(v.begin()); // OK
        foo(v.cbegin()); // ERROR!
    }
 

prog.cpp: In function ‘int main()’:
prog.cpp:29:23: error: no matching function for call to ‘foo(std::vector<int>::const_iterator)’
prog.cpp:29:23: note: candidate is:
prog.cpp:20:10: note: template<class It, typename std::enable_if<(! is_const_iterator<It, void>::value), void>::type* <anonymous> > void foo(It)
prog.cpp:20:10: note:   template argument deduction/substitution failed:
prog.cpp:19:73: error: no type named ‘type’ in ‘struct std::enable_if<false, void>’
prog.cpp:19:73: note: invalid template non-type parameter

Standard output is empty