Re: [boost] [review] Fusion review begins

From: Andreas Pokorny (andreas.pokorny_at_[hidden])
Date: 2006-05-01 13:41:18

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. 

> - 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;
 

> - Are you knowledgeable about the problem domain?

Yes. 

In my opinion fusion-2 should be part of boost. 

Regards
Andreas Pokorny