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From: Joey Mukherjee (joey_at_[hidden])
Date: 2008-06-26 14:43:19

Hi Ron,

This helped a great deal. I have one follow on question:

Suppose this type of setup was within a function, is it possible to
make OneDView the return value of this function? In other words, I
would like to:

array_type::const_array_view <1>::type OneDView;
OneDView = multi_array[myindices];
return OneDView;

In every dimensional case, could I construct my OneDView and save it
to a variable so I have don't have to do the setup every time? The
reason I ask is I have this piece of code in a tight loop and it does
take a bit of time. Maybe there is an easier way to do it?
Alternatively, I suppose I could copy the contents of the slice to
another vector or array?. Is there an easy C++/Boost way to do this?

When I compile the code above, I get a compiler error saying
operator= is private as least that's what I think it is saying!


On Jun 18, 2008, at 11:51 AM, Ronald Garcia wrote:

> Hi Joey,
> I have looked at your self-contained example, so I get the gist of
> what you're trying to do. Rather than assigning to the array view,
> you can assign to an indices object and build the view after the
> fact. Here's how to do the 2-dimensional case that you had
> commented out:
> //This doesn't work, but I would love a
> generic version of this:
> array_type::index_gen::gen_type<1,2>::type
> myindices;
> if (desired_slice [0] == -1)
> myindices = indices [range ()][desired_slice
> [1]];
> else
> if (desired_slice [1] == -1)
> myindices = indices [desired_slice [0]]
> [range ()];
> array_type::const_array_view <1>::type OneDView
> = multi_array[myindices];
> ret_val = (OneDView [whichPosition]);
> HTH,
> ron
> On Jun 14, 2008, at 10:32 AM, Joey Mukherjee wrote:
>> I am trying to use boost::multi_array and want to create a view
>> where I am
>> lowering the number of dimensions, but I wish the dimension to be
>> reduced
>> to be decided at runtime.
>> I have a vector of integers and this vector size is the same as
>> the number
>> of dimensions. If the vector [1] value is -1, then the first
>> dimension
>> will have all values (i.e. range ()), otherwise it will be a number
>> indicating what slice to use.
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