multi_array_ref (lack of) default constructor
Hi, Does anybody know why multi_array_ref doesn't have a default constructor? I'm asking because I wanted to make a multi_array of multi_array_ref and that doesn't seem to be possible because multi_array expect the element type to be default constructible. Thanks, Frank
On Fri, May 29, 2009 at 1:12 PM, gtsml owevwr
Hi,
Does anybody know why multi_array_ref doesn't have a default constructor?
I'm asking because I wanted to make a multi_array of multi_array_ref and that doesn't seem to be possible because multi_array expect the element type to be default constructible.
I don't know, but if it did what would you have it do? Surely it lacks one for the same reason that references must be initialised? - Rob.
I don't know, but if it did what would you have it do? Surely it lacks one for the same reason that references must be initialised?
Yes, that's absolutely right, I just realized that multi_array_ref exactly mimic the C++ ref (probably obvious). I originally thought that multi_array_ref will solve the problem I had with multi_array ownership: the memory chunk I need to work with is already owned by another class. But multi_array_ref is too restrictive for my purpose. As I said, I need to pass a vector of those and that's just not possible. I'm not explaining it too well but the bottom line is that from my perspective multi_array_ref is: - good because it doesn't own the data - bad because it act as a ref: - no default constructor - operator= is a deep copy Ideally, I'm looking for what most people call "a view". Probably playing with words here, but definitely, multi_array_ref is not what I am looking for. Thanks, Frank
On Sun, May 31, 2009 at 2:11 PM, gtsml owevwr
I don't know, but if it did what would you have it do? Surely it lacks one for the same reason that references must be initialised?
Yes, that's absolutely right, I just realized that multi_array_ref exactly mimic the C++ ref (probably obvious).
I originally thought that multi_array_ref will solve the problem I had with multi_array ownership: the memory chunk I need to work with is already owned by another class. But multi_array_ref is too restrictive for my purpose. As I said, I need to pass a vector of those and that's just not possible.
I'm not explaining it too well but the bottom line is that from my perspective multi_array_ref is: - good because it doesn't own the data - bad because it act as a ref: - no default constructor - operator= is a deep copy
Ideally, I'm looking for what most people call "a view". Probably playing with words here, but definitely, multi_array_ref is not what I am looking for.
Perhaps, but multi_array & multi_array_ref do contain the notion of a view. They're used to generate slices through the array, but I think it would be ok to construct a slice which is the whole array, and that would be your view I believe. - Rob. -- ACCU - Professionalism in programming - http://www.accu.org
Perhaps, but multi_array & multi_array_ref do contain the notion of a view. They're used to generate slices through the array, but I think it would be ok to construct a slice which is the whole array, and that would be your view I believe.
That might work actually... Well, at one condition: that the view doesn't hold any reference to the multi_array_ref. Let's put it differently, the view needs to be valid even after the destruction of the multi_array_ref. I'm going to give it a try but please feel free to comment on this as I might be missing something...
Multi_array view has not default constructor, so I'm stuck with the
same problem.
I guess in the end this is a matter of taste. multi_array seems to be
designed so that objects are always valid at all time.
I'm sure it has lots of advantages, still, for lightweight object such
as a view or multi_array_ref, that might not be necessary.
Ok, I think the only solution left is to use pointers to
multi_array_ref, that should work.
I'd be able to do something along that line (not tested):
std::vector<int> memoryChunk0;
std::vector<int> memoryChunk1;
{
std::vector
Could you please explain in more detail the way you're going to use that?
I'm quite new to multi_array, so I am interested in how people apply that.
On Fri, May 29, 2009 at 2:12 PM, gtsml owevwr
Hi,
Does anybody know why multi_array_ref doesn't have a default constructor?
I'm asking because I wanted to make a multi_array of multi_array_ref and that doesn't seem to be possible because multi_array expect the element type to be default constructible.
Thanks, Frank _______________________________________________ Boost-users mailing list Boost-users@lists.boost.org http://lists.boost.org/mailman/listinfo.cgi/boost-users
participants (3)
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Anton Daneyko -
gtsml owevwr -
Robert Jones