On Mon, Sep 1, 2008 at 10:18 AM, Thorsten Ottosen <thorsten.ottosen@dezide.com> wrote:
Giovanni Piero Deretta skrev:
Stacking them naively would have 2^N storage growth, rather than 4^N, and we still don't need to worry about range lifetime.
I've been trying to say that generic algorithms *can't* worry about the range lifetime; they have to assume that the iterators they're passed will not be invalidated before they're destroyed.
I think that the OP is talking about a different problem: let say you want to name the result of stacked applications of range adaptors:
template<typename Range> void my_algo(Range& r) { auto stacked_range = r | filtered(filter) | mapped(mapper); // use stacked_range }
This may lead iterator lifetime problems, not because r iterators may be invalid, but because the iterators of the range returned by filtered(...) may become invalid as that temporary has been destructed.
I don't see how this happens. The iterators are stored by value in each new range that is generated.
But it doesn't need to be so. And that's exactly what all the discussion is about :) -- gpd