cpp/ranges/cartesian product view/iterator/iterator

Construct an iterator.

@1@ Default constructor. Value-initializes the with  and default-initializes the.

@2@ Conversion from to. Initializes with  and  with.

@3@ A private constructor which is used by cartesian_product_view and cartesian_product_view. This constructor is not accessible to users. Initializes with  and  with.