Re: [Boost-users] mpl help

From: David Abrahams (dave_at_[hidden])
Date: 2005-07-06 13:09:38

Zeljko Vrba <zvrba_at_[hidden]> writes:

> David Abrahams wrote:
> |
> | like this one.  If you can condense it into a simple statement, I'm
> | willing to try again, but otherwise I'm not sure I can help you.
> |
> Think UNIX pipelines: ls -l | sort | gzip > /tmp/blah
>
> 1 stage == one operation over the data. ls is provider fo sort which is
> provider to gzip.
>
> i want to mimick the same in C++. each stage consumes data until its
> provider has some, does some processing on the data and feeds the result
> to its consumer (but only when its consumer asks it to provide the data
> - the model is consumer-driven).
>
> but I need more powerful semantic: each stage can have more than one
> input, it can feed its output to more than one stage and types on input
> and output may differ.
>
> is it a bit clearer now?

Seems like you want to build a dataflow machine at compile-time.  It's
a nontrivial problem because, among other things -- since you may have
multiple consumers for any piece of data -- you have to buffer
results.  There aren't any simple answers, AFAICT.

If you have a specific question, I can try to answer, but solving the
whole design problem is beyond my capacity in my "free" time.

-- 
Dave Abrahams
Boost Consulting
www.boost-consulting.com