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From: Eric Niebler (eric_at_[hidden])
Date: 2005-12-02 15:11:32

Andreas Pokorny wrote:
> Hi,
> The default implementation of boost::fusion::pair<first,second> only stores
> an instance of second. I might need a fusion::pair which does not store
> that instance either,

If you want a map with *no* runtime data, then you should use
mpl::map<>, not fusion::map<>. mpl::map<> uses mpl::pair<>, which has no
runtime data. (Caveat: mpl::map is broken in more than one respect at
the moment. Hopefully, it'll be fixed soon.)

> At first I would like to explain what I am doing right now. At
> the moment I do work on an expression template framework, similiar to
> Eric Nieblers boost::proto, which was used to build boost::xpressive.
> I do extend that library by adding a rule system which enables the user
> to define the allowed operations of a certain domain.

Yes, proto needs this. If you're extending proto, I'd gladly accept a patch.

Eric Niebler
Boost Consulting

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