Question

I have a map defined like this

std::map<some_key_type, std::string::iterator> mIteratorMap; 

And a huge string named ‘mHugeString’. Then I walk trough the string collecting iterators like this:

std::string::iterator It=mHugeString.begin(); std::string::iterator EndIt=mHugeString.end(); for(;It!=EndIt;++It){   ...defining a key element...   if(need_to_store_an_iterator)mIteratorMap[key_of_a_right_type]=It; } 

In the end I should recieve a map, where an iterator is associated with a some sort of key. But the iterator somehow looses itself when being paired with a key by ‘make_pair’, unless it points to a place somewhere in the end of a string. It’s hard to tell, but maybe last 256 bytes are fine.

So the question is not how to avoid loosing iterators, it was a stupid idea to store them anyways, but why trying to store an iterator in the begining of the string fails, and why the same with the iterators on the end works fine? What is the difference between them?

Answer 1

I haven’t tried it but I would have expected that, of course you can store iterator values as values in a map.

Do you know that if you change the contents of mHugeString then any iterators into it which you have previously stored are now invalid?

You might choose to store the index into the string, instead of the iterator.