Re: [Boost-users] [fusion] sequence conversion

From: Zeljko Vrba (zvrba_at_[hidden])
Date: 2008-07-20 12:23:13

On Sun, Jul 20, 2008 at 11:36:54AM -0400, David Abrahams wrote:
> 
> Sounds like it's not for you... yet.  One day you will begin to
> appreciate the value of abstraction with performance. Come back and see
> us then :-)  
> 
"Abstraction" might be what is bothering me.. but let's postpone that.  (i.e.
it might be that i'm working on a too concrete level, without planning for
parametrization.. as you've already mentioned.)

> 
> So you no longer wonder?
> 
Well, no :)

> 
> Optimizing iter_swap is hardly premature.  It is a fundamental operation
> that governs the efficiency of many algorithms in the standard library.
> 
Ok, I've never used it myself.

>
> > Well, I *do not know* whether I want to do template metaprogramming in
> > the sense as in your book.  This was the starting point for this whole
> > discussion.  I coded a van-Emde Boas tree via template metaprogramming
> > (simple recursion), and that has had little to do with types.  
> 
> What for?
> 
Hmm, what "what for"?  vEB-tree?  I needed O(lg lg n) priority queue.  Why
metaprogramming: it's a recursive data structure where the same algorithm
is executed at every level, with specialization at 0th level.  It had to
be fast, so I unrolled the recursion at compile-time.

> > OK, thanks.  Anyway, I admire yours and Joels (and others') efforts,
> > but..  let's declare 1:0 in favor of MPL and close the discussion.
> 
> Was there a contest?  Did I miss something?
> 
A figure of speech.  As in, "given my situation and time constraints, I have to
postpone tackling MPL and fusion for later".  I asked about fusion because I've
seen the other mail, and thought it might be easier to start doing something
with it (more precisely: the manual mentions compile-time and *run-time*, and
that made it look "easier").  Now that you've said that it heavily builds on
MPL.. the situation is rather clear: postpone.

> > I'll steer clear of MPL/fusion for a while more.  Maybe the time has
> > come for me to switch to Java, JITs are steadily getting better :-)
> 
> Ohhh... don't do that. Or at least download and read Stepanov's
> "elements of programming" slides before you do.  :-)
> 
Oh, the slides have grown very much lately, thanks for the tip!  (I've browsed
through an early draft of 300-ish pages a while back ago..)