Re: [Boost-users] [fusion] Stateful unary functor for for_each loop

From: Eric Niebler (eric_at_[hidden])
Date: 2007-03-19 17:56:32

Tobias Schwinger wrote:
> Christian Henning wrote:
>> Hi there, is it possible to have a stateful functor object when using
>> fusion::for_each() loop.
>>
>> I would like to to the following:
>>
> <snip code>
> 
> for_each takes the function object by reference to const, so you have to 
> const qualify operator() and make the data members mutable so you can 
> change them anyway.

IMO, this is a bug in Fusion. There should be an overload of for_each 
that takes a function object by non-const reference. Stateful predicates 
should be supported, and Fusion should be explicit about where and when 
predicates are copied, so that the state doesn't get messed up.

-- 
Eric Niebler
Boost Consulting
www.boost-consulting.com