Re: [Boost-users] [range] filtered dereferences underlying range elements twice

Nate, follow is filtered + transformed adaptor's internal behavior. [filtered] increment iterator behavior: while (!pred(*it)) ++it; dereference iterator behavior: *it; [transformed] increment iterator behavior: ++it; dereference iterator behavior: f(*it); [filtered | transformed] increment iterator behavior: while (!pred(*it)) ++it; dereference iterator behavior: f(*it); [transformed | filtered] increment iterator behavior: while (!pred(f(*it))) ++it; dereference iterator behavior: f(*it); oven::memoized is call once function by stored calculation. 2011/6/1 Nathan Ridge :

Thanks Akira, it is good to know that there is a workaround.

But I was wondering, is it necessary in the first place for filtered to dereference the underlying range elements twice?

Thanks, Nate.