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From: Cory Nelson (phrosty_at_[hidden])
Date: 2006-07-01 04:02:19

On 6/28/06, Joaquín Mª López Muñoz <joaquin_at_[hidden]> wrote:
> During some conversations with a colleague I came up with a very
> sketchy realization of what could be converted, if there is interest,
> in a flyweight library. Please see flyweight.hpp at Vault/Patterns:
> The so-called Flyweight Design Pattern, upon which this is inspired,
> is much too OO for current C++ tastes IMHO, what I'm proposing
> takes a more generic stance. A minimal use example follows
> showing the syntax:
> #include "flyweight.hpp"
> #include <string>
> #include <iostream>
> int main()
> {
> using boost::flyweight::flyweight;
> flyweight<std::string> str("hello world");
> std::cout<<str<<"\n";
> }
> Briefly put, a flyweight<T> is an object that can be used as a
> const T (i.e. flyweight<T> provides an operator const T&) but whose
> size is that of a pointer. The trick is that identical flyweight<T>
> objects
> share their representation globally, which drastically reduces memory
> usage when there are much more objects than different values.
> Additionally, comparison of flyweight objects can be made faster than
> that of the underlying type T, since we it reduces to pointer comparison
> --contrast that with what takes to compare the underlinyg type T when
> T=std::string, for instance.
> So, is there interest in having such a lib in Boost? Please note that
> the
> provided implementation is still a primitive one, but OTOH it does have
> all the advertised functionality, so one can use it to test it locally
> and
> form an opinion about its suitability: if somebody, for instance, can
> plug it into some scenario with massive quantities of elements, I'd
> appreciate knowing about resulting memory and performance
> improvements.
> In case this raises interest, I can turn the thing into a more fleshed
> out
> proposal during the summer.

This library seems like it could be excellent, lets get a review going!

As others have noted, of all the languages I have looked at, I've
never heard the term "flyweight", only "interned". Where does
"flyweight" come from? This library might get more recognition if it
used the more common name.

> Thank you for your attention,
> Joaquín M López Muñoz
> Telefónica, Investigación y Desarrollo
> _______________________________________________
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Cory Nelson

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