Re: [Boost-users] [type traits] Extension to operator detection -> choose your preferred naming

Subject: Re: [Boost-users] [type traits] Extension to operator detection -> choose your preferred naming
From: alfC (alfredo.correa_at_[hidden])
Date: 2011-08-29 04:39:53

On Tuesday, August 23, 2011 11:22:45 PM UTC-7, Frédéric Bron wrote:
>
> It is time to include the type trait extension to the official boost trunk.
> These traits can detect if you can use a given operator with given 
> arguments.
>
> For example: has_plus<double, int>::value is true because the
> following program compiles without error:
> double lhs;
> int rhs;
> lhs+rhs;
>

I just want to make the connection with the thread I opened last week: "[math][tools][units] 
generic libraries not generic enough"

The point I want to make is that if there were a uniform facility to deduce 
the result of a built-in operator over some arithmetic types then library 
authors could do a better job at writting generic libraries on some exotic 
arithmetic types and combinations, for example

multiply_typeof_helper<double, int>::type --> double

the name is of course borrowed from boost.Units were it is intesively used:

boost::unit::multiplies_typeof_helper<quantity<si::length>, 
quantity<si::length> >::type --> quantity<si::area>

I just wanted to make the connection between the two problems; and hopeful 
solve the has_operator and typeof_operator problem together.

Alfredo
PS: what if to types can not be multiplied, etc, the has_multiplies will 
tell or multiplies_typeof_helper can return void, or boost::none.

We have come to three proposed lists of names (A, B and C):
> https://svn.boost.org/trac/boost/wiki/GuideLines/Naming/OperatorTraitNames
> I have included the corresponding names of standard keywords, standard
> function objects from <functional>, boost Proto and boost Operators.
>
> Please give your preference between A, B and C before Sept. 5th.
>
> Regards,
>
> Frédéric
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