[boost] Re: Formal Review: Command Line & Config library

From: Chuck Messenger (chuckm_at_[hidden])
Date: 2003-05-27 09:59:35

Vladimir Prus wrote:
> Chuck Messenger wrote:
> 
> 
>>Vladimir Prus wrote:
>>
>>
>>>Yep. This question was raised already. I think that making templates out
>>>of all classes is *a* solution, but I'm not sure it's *the* solution. The
>>>problem is that extensive template usage would prevent making library ---
>>>either shared or static. I think that would be a big downside.
>>
>>Why does that matter?  The great majority of other Boost libraries are
>>header-file-only.  I think of .cpp components of Boost libraries as a
>>sometimes-necessary evil, not as a desired feature.
> 
> 
> Becase header-file-only libraries have two problems --- they increase
> compilation times and they increase binary size. And you can't share the
> code between different applications.
> 
> I think that's important practical aspect. In past, I was burned by
> overgeneralization --- almost all core classes in a program had template
> parameter. It had only one possible value, but I though different ones were
> possible. As the result, compilation time was terrible, and no new possible
> values for the template parameter became needed.
> 
> And these days, I'm rather unhappy with compilation times of BGL...
> 

Perhaps you can do both: write the library with templates for a 
generalized string.  Then, supply "fast.cpp" and "fast.hpp" (choose 
better names).  Use a pimpl idiom in fast.hpp, so it doesn't need to 
include any template code.   fast.cpp includes the templates, but needs 
to be compiled only once.

     - Chuck