Re: [Boost-users] formal review of Switch library ends tomorrow (Wednesday, January 9th) - reviews needed

From: Joel de Guzman (joel_at_[hidden])
Date: 2008-01-11 04:48:38

I almost missed Steven's post. Please post to both lists.

Steven Watanabe wrote:
> AMDG
> 
> Joel de Guzman <joel <at> boost-consulting.com> writes:
> 
>> Single function:
>>
>> I'm a strong advocate of smaller is better. Modularity matters.
>> Big classes (or in this case function objects), metaprogram blobs
>> (i.e. traits), humongous enums, and all such sort of dinosours 
>> are best avoided. They are convenient up to a certain extent and
>> becomes unmanageable beyond a certain limit.
> 
> When it's being managed by humans sure.  When the creation
> of the whatever is automated and it's never used by humans
> directly it doesn't matter much.  The big function object
> you refer to has a single conceptual responsibility.  It isn't
> a blob any more than a fusion sequence used for the same purpose.

Ok. Good point.

>> In all of my use cases, I have N functions that are provided
>> elsewhere and I have no control over (e.g. parser functions).
>> I insist that this is the more common use case. Grouping
>> them into a single big struct is an unnecessary and cumbersome
>> step.
> 
> It may be more common.  What I know for certain is that it's
> slightly easier to implement my interface in terms of yours
> than the other way around.
> 
>> Still, if people insist, I outlined a way to convert the big
>> function object to smaller 'bound' objects, in another post.
>> Just bind 'em into smaller function chunks.
> 
> That's true for your use cases.  For cases where
> you have a runtime integer which you need to convert
> into a compile time integer, which is then used to index
> into an mpl sequence for instance (as in variant)
> separate function objects are pointless.  I don't want
> to relegate this usage to the side just because you
> don't happen to need it.  There are enough use cases
> that it needs to be considered, IMO.  Another example is for
> finite state machines.  Also, at one point I was considering
> a multiple dispatcher that involved a switch.

Yes. I agree. The index is indeed needed. See my latest posts.

Regards,
-- 
Joel de Guzman
http://www.boost-consulting.com
http://spirit.sf.net