[Insight-developers] Templates and preprocessor macros

[Bradley Lowekamp]

With C++0x there is the static_assert:

http://en.wikipedia.org/wiki/C%2B%2B0x#Static_assertions

Which is by far the easiest was to check what you are looking for, as it is just :

static_assert( VImageDimension == 3 );

*poof* compile time assertion. However, this is not supported by all compilers that ITK needs to support so we can't do that for the main code. But if it's just your own project you could use it.

I would be  in favor for adding a itkStaticAssert as a macro to ITKv4. But I am also a meta-programing wacko, so I may be alone. We could use the C++0x implementation if available or fall back to something else, or just do nothing.

Brad

On Jul 11, 2011, at 1:28 PM, Williams, Norman K wrote:

> The only way to solve this is with template metaprogramming.  This makes
> for some extra work getting the syntax right, but you can write the code
> so that it only uses a filter on 3D.
> 
> 
> On the other hand, as one of the people who worked on OrientImageFilter
> back in the day, I don't think anyone should be using OrientImageFilter
> and it should be deprecated, because it destroys information. It only does
> the right thing if all of the direction cosines are aligned with one of
> the world coordinate axes.
> 
> 
> 
> On 7/11/11 11:10 AM, "Benoit Scherrer" <benoitscherrer at gmail.com> wrote:
> 
>> Hi,
>> 
>> Is there a way to use the C++ preprocessor macros that test the value of
>> a template parameter?
>> For example i want to do a generic image filter ( using itk::Image<type,
>> VImageDimension> ) that
>> will use itk::OrientImageFilter only for VImageDimension==3
>> 
>> However, it seems that the preprocessor tool does not 'expand' the
>> templates and
>> just don't know when VImageDimension==3 or not.
>> 
>> Is there any trick to do that, or is it a lost cause ?
>> 
>> Thanks a lot!
>> 
>> Benoit
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> 
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