This is the catchphrase associated with the presentation given by Andrei Alexandrescu during boostcon 2009. I heard about that blasphemy a while ago, but I had neither the time, nor the interest to read it back then.
I finally read it today. You see, I was implementing an incidence graph (as defined by Boost Graph Library) yesterday; to do that one has to write an iterator that, for a given vertex, traverses a sequence of its outgoing edges. Since the graph was potentially very huge, it wasn’t represented explicitly. Instead, the set of adjacent vertices was calculated on-the-fly.
It was quite cumbersome. The amount of state I had to keep inside the iterator was non-trivial, which, while certainly unavoidable, gave me a headache when I realized
- that I’d have to keep the same state twice, once for each bracket of the sequence, and
- that I would have to abuse the state to denote the end-of-sequence marker.
I eventually ended up writing an enumerator that provided
target member functions (which happen to exactly coincide with Alexandrescu’s
front members of the
InputRange concept) that I would use internally and then wrapping it in a pair of iterators for the sake of BGL.
After writing that iterator-from-hell yesterday, I came to the same conclusion as Andrei — iterators should probably be replaced with a more straightforward concept of a range. Ultimately, even my blind devotion to C++ and STL design didn’t prevent me from agreeing with the slides on almost all accounts.