Re: [Boost-users] [BGL] Implementing own graph types: Overloading in namespace boost or ADL?

Subject: Re: [Boost-users] [BGL] Implementing own graph types: Overloading in namespace boost or ADL?
From: Jeremiah Willcock (jewillco_at_[hidden])
Date: 2012-03-23 16:10:17

On Fri, 23 Mar 2012, Philipp Moeller wrote:

> Jeremiah Willcock <jewillco_at_[hidden]> writes:
>
>> On Fri, 23 Mar 2012, Philipp Moeller wrote:
>>
>>> The documentation does not explicitly mention which of both approaches
>>> is recommended to implement the free function of the graph concepts for
>>> a custom graph. Usually the graph will be in its own namespace.
>>>
>>> Should the free functions be declared in the boost namespace or in the
>>> same namespace as the graph?
>>
>> In the same namespace as the graph.
>
> Maybe that should be stated explicitly somewhere.

OK.  That is the general rule for defining functions to use with generic 
libraries (for example, operators for iterators).

>>
>>> This also would determine if BGL functions should be called qualified or
>>> unqualified outside of namespace boost.
>>
>> They should be called unqualified; I try to make sure that examples do
>> that so that they will work on user-defined graph types.
>
> The LEDA example [1] does exactly the opposite. Probably that would be a
> good start.

The problem there is that C++ doesn't have good ways to adapt third-party 
libraries to work together without adding things into the namespace of one 
of the libraries.  The correct way to write that example would be to put 
the functions into the LEDA namespace so that they can be found by ADL.

-- Jeremiah Willcock