cpp/iterator/counted iterator/counted iterator

Constructs a new iterator adaptor.

@1@ Default constructor. Value-initializes the underlying iterator and initialized the underlying length with. Operations on the resulting iterator have defined behavior if and only if the corresponding operations on a value-initialized also have defined behavior.

@2@ The underlying iterator is initialized with and the underlying length is initialized with. The behavior is undefined if is negative.

@3@ The underlying iterator and length are initialized with those of.