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From: Joel de Guzman (joel_at_[hidden])
Date: 2006-05-02 02:38:59

Andreas Pokorny wrote:
> On Mon, May 01, 2006 at 09:49:52AM -0400, Ronald Garcia <garcia_at_[hidden]> wrote:
>> - What is your evaluation of the design?
> Well done, it is both clean and extensible.
> I do like the separation of metafunctions yielding the result of an
> operation in the dedicated result_of namespace and the runtime functions
> in the plain fusion namespace.
> But I would like to emphasize the laziness of the algorithms. It allowed
> me to store fusions pair types, and a self written compile time only ct_pair,
> which does not have an instance of the second(value) type, in the
> associative map tuple container. Operating on the different pair types
> does not cause any problems. Only trying to dereference an iterator
> pointing on a ct_pair to access the value will cause compile errors.
> By applying a simple filter it is still possible to access all (runtime)
> values of the tuple.
> In the end I was able to store information existing during run and compile time
> and compile time only information inside a fusion tuple.

That's in my TODO list: formalize the "pair" concept. Right now,
the docs mention using fusion::pair, yet as you've mentioned,
fusion::map is not really hardwired to require it. It can use any
"pair" as long as it conforms to the concept (even std::pair[**]
or mpl::pair might do ok (AFAICT, but untested)).

[**] This might be useful because I am now aware of some cases where
you need to attach some runtime data to the keys.

>> - What is your evaluation of the implementation?
> The code is clean - readable. I learned using fusion-2 by reading the formerly
> sparse or non existing docs and the source code. It took me some time understanding
> the dispatching system, but right after that everything turned out to be
> clear and obvious.
> I am using fusion from spirits cvs for several months now. In all that
> time I detected only one bug, which got fixed within hours.
>> - What is your evaluation of the documentation?
> The entry pages are fine to read, the reference is complete.
> But I think someone new to type sequences, could need a more detailed
> documentation.


>> - What is your evaluation of the potential usefulness of the library?
> Very useful. In my opinion it is a must-have for boost.
>> - Did you try to use the library? With what compiler?
>> Did you have any problems?
> I currently write a dsl framework using fusion, with a domain specific
> rule system. Fusion maps are used to store node attributes in the expression
> tree. I used different versions of gcc to compile.
> Apart from a gcc linker bug that shows up in a certain version of
> binutils, and with certain locale settings, I had no problems.
> I wonder if there are compiler limitations in symbol name lengths.
>> - How much effort did you put into your evaluation? A glance? A
>> quick reading? In-depth study?
> Nearly an in depth study, since I learned fusion-2 by reading the source
> code. When reading the documentation today I discovered several nice features
> like the vector_tie, allowing something like
> int i; char c; double d;
> vector_tie(i, c, d) = make_vector(1,'a', 5.5);
> which is nearly as cool as:
> int i; char c; double d;
> i,c,d = 1, 'a', 5.5;

That part is taken from the Boost.Tuple docs, for which I should
give proper credit. Right now, there's a simple acknowledgment to
Jaakko, its author. I should mention too that he, and Jeremiah
Willcock were also involved in Fusion coding in its early days
when it started as a TR1 implementation of tuples.

>> - Are you knowledgeable about the problem domain?
> Yes.
> In my opinion fusion-2 should be part of boost.

Thank you very much and thank you for your review.


Joel de Guzman

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