[boost] [Proto] review

From: news.gmane.org (david_at_[hidden])
Date: 2008-03-02 14:30:34

> Please always state in your review, whether you think the library should 
> be
> accepted as a Boost library!

Yes, Proto should definitely be accepted.  It is a very useful foundation 
tool for building a DSEL with efficient execution performance.

> - What is your evaluation of the design?

The design is very clean and well thought out.  This is Eric's second 
version of Proto and he obviously learned valuable lessons from the earlier 
version(s).

> - What is your evaluation of the implementation?

I read through much of the code and while I can't claim to understand it 
all, it seems well written.

Would it be possible to eliminate the need for dummy parameters in examples 
like "make_pair_(1, 3.14), j, j )", where the state and visitor parameters 
are not used?

In many places I see "when<_, xxx>" to mean transform anything to xxx.  Is 
there an advantage to this syntax or would "always<xxx>" be simpler?

> - What is your evaluation of the documentation?

The documentation is good with many examples, but it took me several 
readings to "get it".

I would like to see a section on debugging strategies and examples, 
particularly for Proto transforms.  The display_expr() function could be 
documented with an example.  Is there a way to create a "trace" of compiler 
messages, for something like the CalcArity example, where the compiler 
outputs warning messages as it does the mpl::max comparisons?  I tried using 
techniques from the "C++ Template Metaprogramming" book, but couldn't get it 
to work.  Any tools or techniques to help debugging would be appreciated.

I couldn't find definitions for macros like BOOST_PROTO_EXTENDS_xxx, 
BOOST_PROTO_DEFINE_OPERATIONS, and BOOST_PROTO_AUTO.  Also, 
proto::pod_generator isn't described anywhere.

It would be helpful if the Concepts section were expanded with more 
definitions, because I kept getting confused about the precise meaning of 
grammar, transform, pattern, context, domain, generator, etc.

> - What is your evaluation of the potential usefulness of the library?

It will be useful in a variety of problem domains, where it's important to 
define a clean syntax to a high-performance implementation.  However, the 
effort needed to understand Proto and write and debug code for it is a 
significant consideration.

> - Did you try to use the library?  With what compiler?  Did you have any
> problems?

 I wrote some small test cases and they ran well. The only problem I had was 
a proto::flatten test case that caused a "C1001 internal compiler error" on 
the msvc9.0 compiler.  I sent this test case to Eric.

> - How much effort did you put into your evaluation? A glance? A quick
> reading? In-depth study?

I've been following Proto for over a year.  I spent about two days reviewing 
the current version.

> - Are you knowledgeable about the problem domain?

Yes, somewhat.  I've written some test cases but haven't tried a real 
application.