Re: [sigc] conditions in libsigc

[Paul Pogonyshev <pogonyshev gmx net>]

Chris Vine wrote:
> > Not really if they are not implemented in the libraries, because then
> > implementing conditions costs more than they save.  If, however, conditions
> > are implemented in the libraries, I'm sure it is worth it, saves coding for
> > library users and makes error probability smaller.
> 
> My comments assumed it was implemented in the library.  The choice is between 
> three lines of code and, as I said and you agree, writing implementation 
> classes for each condition derived from condition_impl.

Three lines of code are repeated many times in each program using Glibmm.
Besides, there is another reason: encapsulation gives smaller error
probability.

> > > Your approach is also rather inflexible - it can only synthesise from two
> > > states.
> >
> > Yes, conditions cannot solve all problems.  If you need some advanced
> > checking, you should use traditional scheme, which doesn't go away. 
> > However, I'm sure that 75% of appropriate tasks are solvable with
> > `standard' conditions.
> 
> With a certain sense of deja vu, this would be relevant to gtkmm rather than 
> the libsigc++ library (yes, I know you want the substructure in libsigc++, 
> but I am talking about the condition implementation classes here, which is 
> what is relevant to any "standard" conditions you propose).  Furthermore, in 
> my opinion (I accept not in yours) I doubt that there are sufficient 
> synthesised conditions not already in gtkmm which are suitable as a standard.

I mentioned that conditions are simply convenient wrappers around signals, they
give nothing new.

Alas, I haven't heard from sigc++ maintainer so far :(

Paul