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Subject: Re: [boost] [review] Multiprecision review scheduled for June 8th - 17th, 2012
From: John Maddock (boost.regex_at_[hidden])
Date: 2012-06-05 12:54:02

>> * non-member functions are required if defaults are to be provided for
>> the
>> optional requirements.
>> * There are some non-members that can't be written as overloaded
>> non-member operators but can named free functions (sorry I forget which
>> ones, but I remember seeing one or two along the way).
>> * explicit conversions aren't well supported at present.
>> * Compiler bug workaround (older GCC versions), there's a note at the
>> requirements section: "The non-member functions are all named with an
>> "eval_" prefix to avoid conflicts with template classes of the same
>> name -
>> in point of fact this naming convention shouldn't be necessary, but
>> rather
>> works around some compiler bugs. "
> One alternative to using a collection of free functions and metafunctions
> to extend an interface for a given type is to first mediate this
> customization via a traits class with static member functions and nested
> typedefs and metafunctions. Indeed, the default implementation of the
> traits class would just use the (perhaps overridden) free functions. John:
> Have you considered this extra level of indirection, or do you have any
> comments on this?

No, but from a purely practical point of view, I believe the free function
approach is easier for both the lib developer and a backend developer -
overloading free functions is easy to do and the overload resolution rules
well understood I believe. In addition if someone wants to experiment with
modifying an existing backend, then extending it's functionality by
providing additional function overloads is simple, and requires no
modification to the original header.


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