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Subject: Re: [Boost-users] Best way to put N ranges into a new container?
From: Mathias Gaunard (mathias.gaunard_at_[hidden])
Date: 2010-07-07 17:49:56

Le 07/07/2010 17:36, John Dlugosz a écrit :

> After pondering something like join(join(R1,R2),R3), I realized that the whole idea, while it would make functional programming guys smile, is inefficient. Iterating the joined range and copying one element at a time, with overhead to look for boundaries, will prevent the container's optimized push_back from being called with a range of contiguous memory of trivial items.
> So, I really want something that will call that form for the ranges. Now I'm thinking of a metaprogram like used for matrix math, to collect the N-ary concats and then apply them when the final thing is converted to a vector.
> Really, I'd like an "Assign" that uses such techniques instead of throwing everything into a deque and then copying it.

The constructor of vector and its assign member function are already
optimized to exploit random access iterators.

Note however that a joined range of random access ranges doesn't know
that every joined range is the same size, so its random access features
are a bit slow.

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