Re: [boost] Interest for a perl6-like-junctions-class?

From: Rob Stewart (stewart_at_[hidden])
Date: 2005-07-24 16:12:41

From: FlSt_at_[hidden]
> 
> The new Perl 6 has a nice feature called junctions. See 
> http://www.perl.com/pub/a/2003/07/29/exegesis6.html?page=4 and
> http://www.metaperl.com/talks/p6-junctions/ for more information. I 
> think this is a interesting way to save the time for writing loops in 
> some situations. I've tried to implement this for C++ and uploaded a 
> version with two examples into the Boost Sandbox File Vault 
> (flos_super_position.zip). This version works for my purposes, but if 
> you interested i would rework it and submit it to the boost library.

I have a few questions about your design:

   Why "super position" versus Perl's "junction?"  When
   describing the enumerators, you use the Perl terminology,
   apparently because it makes sense.  Frankly, I don't "get"
   "super position."

   Why is the junction type a template parameter?  Did you
   consider making four separate types?  Does using one make it
   easier to compare instances of the four types?  Should the
   client have to care about that?  IOW, I think writing
   disjunction<T> is simpler and clearer than
   super_position<ANY, T>.  Other name possibilities like
   "any_of" are possible, too.

   Why would one change the Container parameter?  Why would the
   client of this class care about the associative container
   being used to implement it?

I noted that you wrote your loops to repeatedly evaluate x.end().
Algorithms avoid that problem; if you need your own loops, you
should hoist calls to end() out of the loop.

-- 
Rob Stewart                           stewart_at_[hidden]
Software Engineer                     http://www.sig.com
Susquehanna International Group, LLP  using std::disclaimer;