Check if a variable type is iterable?

Question

Is there any way to check if an arbitrary variable type is iterable?

So to check if it has indexed elements or I can actually loop over it\'s children? (Use foreach

Answer 1

It depends on what you mean by "iterable". It is a loose concept in C++ since you could implement iterators in many different ways.

If by foreach you're referring to C++11's range-based for loops, the type needs begin() and end() methods to be defined and to return iterators that respond to operator!=, operator++ and operator*.

If you mean Boost's BOOST_FOREACH helper, then see BOOST_FOREACH Extensibility.

If in your design you have a common interface that all iterable containers inherit from, then you could use C++11's std::is_base_of:

struct A : IterableInterface {}
struct B {}
template 
constexpr bool is_iterable() {
    return std::is_base_of::value;
}
is_iterable(); // true
is_iterable(); // false