[Boost-users] Re: Using MPL towriteis_derived_from_std_basic_ostream

"David Abrahams" wrote in message:

"Jonathan Turkanis" writes:

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"David Abrahams" wrote in message

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It's hard for me to understand why you would need has_xxx for this purpose, or how you would use it.

Well, you could look at the attachment .... ;-)

I did, but got mired in details.

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Why not just copy the implementation of is_base_and_derived and templatize the conversion operators in the Host class?

I thought of that. I liked the posted version because it just uses out-of-the box components. Maybe it just doesn't look mired in details to me because I wrote it :-). BTW, the first macro BOOST_IO_BOOL_TRAIT_DEF in the attachement is not relevant to the current discussion. The macro BOOST_IO_IOS_TRAIT_DEF conatins the entire implementation of the above technique. Jonathan