Re: [pooma-dev] Is Default Constructable really required?

[Jeffrey Oldham]

On Thu, Mar 07, 2002 at 05:36:37PM -0700, John H. Hall wrote:
> Gang:
> In the notes on Relations (in relations.h, copied below) it states "The 
> RelationFunctor must be Default Constructable...", yet from the use of 
> it, I don't see any actual requirement for this. It seems we just pass 
> around const references and use the alternate required constructor 
> mentioned below, along with a copy constructor. I need to set up some 
> state in my RelationFunctors and I would prefer to do it during 
> construction, along with providing the correct copy constructors and a 
> version of this required constructor which is essentially a copy 
> constructor++.
> 
> So I guess my question boils down to: "How do I set and keep state in 
> RelationFunctors?" Any non-trivial use of Relations will require this.

I concur with your analysis.  See src/Field/Relations/PeriodicFaceBC.h
for an example.  It does not have a default constructor but does have
a non-default, non-copy constructor.

I have attached a patch aligning the comments to the extant source
code.  Would someone (Scott? Stephen?) approve these changes?  I also
added the (gratituous) change of s/L/Target/.

Thanks,
Jeffrey D. Oldham
address@hidden

2002Mar11  Jeffrey D. Oldham  <address@hidden>

        This patch corrects functor requirement comments and improves them
        by replacing "L" by "Target".
        
        * Relations.h (Relation[0-6]): Change introductory comment, replacing
        "Default Constructable" with "Copy Constructible."  Change
        constructor specification to list "RelationFunctor" first.  Change
        "L" to "Target".
        (RelationFunctionPtr[0-6]): Change template parameter's name from
        "L" to "Target".
        (RelationMemberPtr[0-6]): Likewise.
        (newRelation): Likewise.
        (functionPtr): Likewise.
        (memberPtr): Likewise.

Tested on sequential Linux using g++ by compiling Pooma library and
        running all Field tests.
Approved by     ??you??
Applied to      mainline

Relations-comments.patch
Description: Text document