Based on C ++ 11 range for range (L, R)

Question

C ++ 11 does not have a range-based loop for a coherent sequence.

for(auto e : {0..10} ) // wouldn't compile!!! 

So, I just decided to imitate it.

 template< class T , bool enable = std::is_integral<T>::value > struct range_impl { struct iterator { constexpr T operator * ()const noexcept { return value; } iterator& operator ++()noexcept { ++value; return *this; } friend constexpr bool operator != (const iterator & lhs, const iterator rhs ) noexcept { return lhs.value != rhs.value; } T value; }; constexpr iterator begin()const noexcept { return { first }; } constexpr iterator end ()const noexcept { return { last }; } T first; T last ; }; template< class T > range_impl<T> range(T first , T last) noexcept { return {first, last}; } int main(){ // print numbers in [ 0..10 ), ie 0 1 2 3 4 5 6 7 8 9 for(auto e : range(0,10) ) std::cout << e << ' '; std::cout << std::endl; } 

Q: How to generalize this method to ForwardIterators?

Example:

 template< class ForwardIterator, class T > bool find(ForwardIterator first, ForwardIterator last, T const& value) { for(auto e: range(first, last) ) if (e == v) return true; return false; } 

Answer 1

Specialization

 template< class Iterator> struct range_impl<Iterator, false> { range_impl(Iterator first, Iterator last) : first(first), last(last) {} constexpr Iterator begin()const noexcept { return { first }; } constexpr Iterator end ()const noexcept { return { last }; } Iterator first; Iterator last ; }; 

Test

 int main(){ for(auto e : range(0,10) ) std::cout << e << ' '; std::cout << std::endl; const char* a[] = { "Say", "hello", "to", "the", "world" }; for(auto e : range(a, a + 5) ) std::cout << e << ' '; std::cout << std::endl; } 

Answer 2

You are trying to override boost::iterator_range and boost::counting_iterator . Just do it instead:

 template< class T > boost::iterator_range< boost::counting_iterator<T> > range( T const& tBegin, T const& tEnd ) { return boost::iterator_range< boost::counting_iterator<T> >( tBegin, tEnd ); } 

Even boost::counting_range already exists: http://www.boost.org/doc/libs/1_47_0/libs/range/doc/html/range/reference/ranges/counting_range.html