Hello all,
I have recently reviewed the Boost presentation put together by Matthew and intend to present it to my peers also. It was especially welcome to see this because I've been wanting to present to my peers on Boost for awhile but haven't had the time to learn enough about the library to put a presentation together. So, something I wanted fell right in my lap! Kinda like finding a $100 bill on the street!
I do have one question about the array library. In the documentation, the statement is made that the advantage array has over vector is the fact
Hi Dave,
Vector is more flexible than array. But this flexibility comes at a cost.
Even if you reserve space for a known number of elements, vector cannot
assume that you won't add or remove elements. So there's a minor overhead
in keeping track of when it needs to expand if you choose to add more
elements.
Also, reserving elements for a vector only guarantees that space for _at
least_ that number of elements is reserved (see 23.2.4.2 in the standard) -
it may in fact reserve more in the hope that it won't need to reallocate in
the event you choose to add more elements. So it may consume more memory.
Boost::array can avoid all of those potential issues because you specify the
number of elements at compile-time and it cannot change.
But the main reason to use boost::arrays IMHO is for clarity. If you know
how many elements are required they let you express that clearly - something
that neither vector nor standard arrays can do. This is of particular
advantage when you consider passing a container with n elements to a
function:
void thisFunctionRequiresA10ElementArray(const boost::array
since vectors provide the semantics of dynamic arrays, "This results in some overhead in case only arrays with static sizes are needed.". When discussing this with my peers, I'd like to present something a little more concrete to them.
If I have a number of elements that is known at compile time, why, *specifically*, should I prefer boost::array to std::vector?
Thanks! Dave