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Subject: Re: [boost] Case study: Boost.Local versus Boost.Phoenix
From: Joel de Guzman (joel_at_[hidden])
Date: 2011-02-03 23:04:24

On 2/4/2011 10:36 AM, Gregory Crosswhite wrote:
> In conclusion, I have found that Boost.Phoenix is simply too painful to use in practice
> for most cases where I have been using Boost.Local. Although it could potentially allow
> for very elegant code in many cases, it is so hard to figure out what you are doing wrong
> that it seems to be more trouble than it is worth. I am actually a little sad at having
> arrived at this conclusion, because the library looked incredibly cool and I was very
> excited about trying it out, and now I am just walking away from the whole experience
> feeling incredibly frustrated. Furthermore, even if I were an expert in it I have trouble
> seeing how in most of the places in my code it would result in code that was either more
> clear or easier to write. The Boost.Local code has extra noise at the beginning, but when
> the main body of the nested function contains lots of calls it is far more expressive to
> write the C++ code directly than to use lots of pheonix::bind functions to accomplish the
> same thing.
> This doesn't mean that I think that Boost.Phoenix is a bad library. Reading through the
> documentation I am absolutely amazed at how it can be used to create very expressive
> functions; the authors have clearly worked very hard on it and should be proud of their
> work. However, it simply cannot be treated as invaliding the need for something like
> Boost.Local, because for one to accomplish many of the same tasks in Boost.Phoenix as one
> can accomplish in Boost.Local one has to deal with a whole lot of extra mental effort and
> frustration, and the result at the end is often less expressive and clear (and potentially
> less maintainable) as it would have been if one had used Boost.Local since the body is no
> longer expressed in standard C++.

You've just scratched the surface, and IMO, learned about the library in
a way that I would not advice. To be honest, I never liked bind -- not a
bit. If I did it my way, I'd write small modular phoenix functions
just like you would in C++ or any FP language, but are fully curryable
and lazy. It's very similar to what Local provides, albeit in C++ syntax
instead of macros. By doing so, you avoid overly complex phoenix expressions
and work closer to C++ but at the same time get all the benefits of FP.

As I hinted, it is also possible to provide Local like macros to make
the code even more concise. Right now, admittedly, phoenix function is
more verbose, but it does a lot more and is more flexible.


Joel de Guzman

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