abir basak wrote:
shunsuke wrote:
So there are 3 library I am searching, 1) Index -> iterator , and iterator -> index conversion (I know that 2 famous facts in STL that iterator doesn't know container and their position, but that is only applicable for pointers . There is no harm to know this facts from iterator. and thus some library can do to-from conversion between iterator & index position , or better sub_range & pair<index_t,index_t> any library ? Boost has 'counting_iterator'. http://www.boost.org/libs/iterator/doc/counting_iterator.html You can call 'counting_iterator::base()' if you want the 'index'.
Here I am not getting the "index" from counting_iterator. std::vector<int> v; v+= 1,2,3,4,5,6,7,8,9,10; std::for_each(v.begin(),v.end(),std::cout<<_1<<" "); counting_iterator<std::vector<int>::iterator > it_b = make_counting_iterator(v.begin()+3); std::cout<<*it_b.base(); /// This prints the element at that pos i.e 4, not the position, i.e 3 . How to get the index back from iterator ?
Boost doens't have such iterator, AFAIK. You maybe need to write one from scratch, holding 'v.begin()' or something.
3) an utility which allows to refer a portion (or some portions ) of a container to be stored ( i.e store by index & return by iterator ) inside another class , using the above two library .... If you take the portions represented by different types into a single deque, Dr.Becker's 'any_iterator' is a candidate. http://thbecker.net/free_software_utilities/type_erasure_for_cpp_iterators/s... At present I don't need a polymorphic or heterogeneous iterator. I am looking at it.
You try to use an iterator through the "index". That is a polymorphism. :-)
And also looking at some iterator adapter (or range ) which can be stored inside a class or another container. i.e it will perform all of the operations using index & a reference to the container internally. Thus it needs to know the container & the position in the container. can any_iterator or some other be stored (or boost::sub_range of those iterator adapter) inside a class , or I need to store index and construct iterator with the help of container.
After all, the index seems to behave as the type erasure. 'any_iterator' is the most generic one to do it. (You may recall a battle of switch vs virtual.) On the other hand, it is difficult to implement 'any_iterator'. An iterator tracking its own index can be a reasonable solution. Regards, -- Shunsuke Sogame