On Friday 16 February 2007 16:09 pm, you wrote:
Such a combiner would violate the single pass traversal limitation of the input iterator concept. The cache solution allows dereferencing the same iterator multiple times to acquire the same value without calling the slot again, which already is a stronger guarantee than an input iterator usually provides. The combiner example in the docs makes use of it.
Timmo,
Thanks for you reply. I don't think I'm violating anything spelled out in the single pass traversal requirements (maybe violating the spirit but not the letter).
Oh, nevermind. Now I see the line in the docs for the input iterator concept that would be violated: [3] After executing ++i, it is not required that copies of the old value of i be dereferenceable or that they be in the domain of operator==. -- Frank