[Insight-developers] ConceptCheck & Wrapping : ITK 3.4 Update

[Brad King]

Luis Ibanez wrote:
> 
> 
> This sounds indeed like the right thing to do,...
> *for one release*...
> 
>    but...
> 
> 
> We shouln'd understimate the cost/effort of maintaning
> such a system for the next five to ten years.

I agree that the technique is not that maintainable.  It is just an
example of how to implement full compatibility without allowing new code
to use the old behavior.

There are two kinds of compatibility: feature compatibility and "bug
compatibility".  The case discussed in this thread is a bug
compatibility issue.  We have replaced a subtle runtime bug (integer
truncation of results) with an explicit compile-time message.  One could
argue that this change is a feature enhancement.  I think less effort
should be spent on bug compatibility.  As long as the breakages are
documented the fixes should not be a problem.

Going back to Bill L's young grad student example, if he/she has been
given the task of updating an application to use a new ITK release, then
the task inherently involves dealing with issues like the resulting
error message.  If the application has been working well for years with
an older ITK, then why upgrade?  Obviously in order to get some new
features.  The cost of getting the new features is a couple minutes
fixing a few compiler errors on code that had a bug anyway.

-Brad